Assembling Zynthian Kit V5.1

1 Previous Requirements

1.1 BOM V5.1 kit

• V5.1 Aluminum Case
  • Bottom
  • Top
• Main Board
• Control Board
• Display
• Raspberry Pi5
• Thermal Block
• Thermal Pad (1 piece of 6 x 2 cm)
• Silicone Keypad
• Rubber Feet (4 units)
• Wiring
  • RBPi5 DSI display flat cable: 20cm long, 1.6cm wide, 1mm/0.5mm pitch, black or orange
  • Control Board flat cable: 15cm long, 1cm wide, 0.5mm pitch, black or grey
  • USB-C adapter + flat cable: 5cm long, 1cm wide, 0.5mm pitch, black or grey
  • uSD-card adapter with flat cable: 5cm long, 1cm wide, 1mm pitch, grey
• Screws
  • 12 x ISO7380 M2.5x5mm black zinc-plated steel (the smaller ones with round head)
  • 21 x ISO7380 M3x5mm black zinc-plated steel (the slighty bigger ones with round head)
  • 10 x DIN7991 M3x6mm black zinc-plated steel (the ones with conic head)
  • 4 x DIN916 M3x4mm black zinc-plated steel (the headless ones)
  • 8 x Hexagonal Spacer M3x10mm brass
• Mechanized Aluminum Knobs (4 units)
• Power Supply: 24V, 1.5 Amp (1 unit)
• SD-Card >= 32GB (NOT included in V5.1 kit)
• Optional: CR2032 lithium battery (NOT included in V5.1 kit)

WARNING!!

For working, the V5.1 needs a SD-card with the ZynthianOS software. Learn how to download the SD-image and prepare your SD-card.

1.2 Tools Required

• Allen Spanner 1.5 mm
• Allen Spanner 2.0 mm
• Scissors or Cutter (NOT included in V5 kit)
• Rule meter (NOT included in V5 kit)

1.3 Time Required

Depending on your skills and ability it may take 1 to 3 hours.

2 General Advice

• Read and follow carefully the assembling instructions. Don't ignore any guidance or recommendations. We are quite lazybones, so we should have had some important reason to write them.

• Use the browser's zoom to magnify the details in the pictures. They have good resolution and will allow you to see all details you need.

• Prepare the working space and the needed tools. A clean 120 x 60 cm table will be big enough. More is always welcome. Less is not recommended. Remove all stuff you don't need from the surface and prepare the tools you will need.

• Ensure you have good lighting in the working area. Having good lightning will ease delicate operations, especially those involving smaller parts.

• Please, be extremely delicate when manipulating the flat cable connectors (FPC). They are the weakest parts and can be easily broken. Look carefully at the photos/videos and proceed just in the way we recommend. Use 2 hands, one finger from each hand. Avoid manipulating the connectors with a single hand or finger and don't use any tool for this.

• Don't be impatient. If you have doubts or you don't know how to go on, please, stop assembling and ask in the forum or send an email to support@zynthian.org. It's better to wait some hours to get an answer than waiting for days/weeks to get a replacement part.

• Keep your hands clean so you can enjoy a nice unit after finishing.

WARNING!!

DON'T USE FORCE! NEVER! Some parts are really delicate, especially flat cable connectors (FPC), and you can easily break something if you are brute. Assembling the V5 unit is not difficult at all, but it's a clock-maker work. A beginners one that almost everyone can do, but clock-maker's task anyway. If you are not very used to manipulate this kind of stuff, please, proceed slowly. Thinking twice will let you build it once.

3 BOTTOM PART

3.1 Dump the screws from the bag in a suitable receptacle

Be careful when opening the screws bag. Some of them are really small and you can easily lose them. Please, don't dump them on the table's surface or on top a piece of paper. We recommend to dump the bag's content in a small tray, so you can look at and take out the parts easily while getting them well confined so they can't be lost.

Pay special attention to the 4 tiny headless screws used to secure the knobs. They are really small!! You can screw them into the knobs as a first step to avoid losing them during the build process.

Now is a good time to familiarize yourself with the different screw models available. Take a close look at the content of the screws bag and try to identify:

• 12 x ISO7380 M2.5x5mm black zinc-plated steel => the smaller ones with round head
• 21 x ISO7380 M3x5mm black zinc-plated steel => the slighty bigger ones with round head
• 10 x DIN7991 M3x6mm black zinc-plated steel => the ones with cone-shaped head
• 4 x DIN916 M3x4mm black zinc-plated steel => the headless ones
• 8 x Hexagonal Spacer M3x10mm brass => they are the only brass parts

3.2 Stick the rubber feet to the aluminum case bottom

1. Look for the aluminum case bottom part in the "V5" case package:

2. Look for the 4 x rubber feet inside the wiring bag, in the "Screen and Bits" case:

3. Stick the 4 x rubber feet to the aluminum case bottom part. This will prevent scratches during the assembly process.

3.3 Plug the display ribbon cable into the RPi5

1. Look for the display ribbon cable in the "Screen and Bits" case. It's not inside any plastic bag but it's laying in the cardboard box. It's 20cm long and 1.6cm wide, having different terminations on each side. Most probably it will be labeled as "Display cable 200mm", white text over black or orange cable.

2. Look for the RPi5 in the "Accessories" case.

3. Open the RPi5's DSI connector by softly pulling up on both sides of the tiny black/grey tongue at once. It opens only about 2mm. When it's totally open, push the ribbon cable inside, straight down, with the black shiny side at the end of the cable facing out (towards the HDMI printed on the RPi5 board). The contacts on the end of the cable that are pushed into the connector should be facing the RPi5 Ethernet socket, while taking care to have the black shiny side facing away from the Ethernet socket. When the cable is tightly inserted, close the connector by pushing down on the tongue with 2 fingers, one of each hand. Pay attention to ensure the cable does not move out of the connector. If it's not well inserted or not straight, repeat the operation until it's OK.

WARNING!!

When possible, use 2 hands to manipulate the fragile FPC connectors. You will control the applied force a lot better compared to just using a single hand. If you can't use both hands, take extreme care. Indeed, you should always take extreme care while manipulating FPC connectors.

Note:

If you break an FPC's connector tongue, you could work around the problem using a hot glue gun. Not nice, but it works quite well!

3.4 Install the thermal block

The RBPi5 has a fast CPU that runs at 2.3 GHz and we need to remove the heat generated by its components. As we don't want a noisy fan, prone to failure, pushing dust inside our nice case, we are using the aluminum case as a huge heat-sink. This is achieved by the thermal block, a solid aluminum block that closely contacts with the RPi5's chips and serves as a heat-highway to the aluminum case bottom, and from there, to the rest of the aluminum case. When your zynthian V5.1 is working hard, or when external temperature is high enough, you will note the aluminum case getting hot. This is good because it means the thermal block is doing its job of transferring heat from the inside to the aluminum case body, where it's dissipated to the ambient environment.

Zynthian V5.1 could get a 20% extra power from the RPi5 by overclocking the CPU up to 3 GHz. By default overclocking is disabled because not all RPi5 boards support overclocking, but you can try, and luckily, you will get an extra power boost. Obviously, installing correctly the thermal block will increase the chance of overclocking successfully your zynthian.

Having understood all this, you may realize this is a key step for getting your V5.1 working at 100% (or more!) of its capacity, so don't be in a hurry and take your time to do a good job. Let's start!

---

1. Look for the thermal block in the accessories case.

2. Look for the piece of thermal pad in the wiring bag, in the "Screen and Bits" case. It is a piece of approximate size of 60 x 20 mm, gray on one side and blue on the other.

3. Using the rule-meter and the scissors or cutter, cut 4 little pieces of thermal pad with these apr sizes:

• 20 x 28 mm
• 19 x 12 mm => This is the most important!
• 14 x 9 mm
• 11 x 11 mm

4. Remove the blue protective sheet from the 3 smaller pieces and stick them to the inner side of the thermal block, the one that makes contact with the RPi5. You'll recognize it because it has 3 small rectangular islands that fit the size of the 3 smaller pieces you cut out. You can use your finger to stick it, pressing and extending the thermal pad. Use your fingernail to cut off the excess, if any.

5. Take 4 x ISO7380 M2.5 screws. They are the smaller ones with rounded head.

6. Remove the transparent protective sheet from the 3 pieces of thermal pad and fix the RBPi4 compute module to the thermal block using the 4 x ISO7380 M2.5 screws.

7. Before installing the "RPi5 + thermal block" assembly in the main board, you must fold the display cable adequately, so it goes in the right direction. You must fold it twice, putting attention to the pictures and using your "common sense". The first fold is straight and the second one is at 45º, so you get the cable going out the RPi5 with the text "Display-cable-200mm" on the down side. We show several pictures from different angles. Zoom in as needed until you have clear how to proceed. Take your time and think twice to do once.

8. Finally, stick the remaining piece of thermal pad (27 x 20 mm) on the contact surface in the external side of the thermal block. That is, on top of the big "tower" with 2 tiny holes. Follow the same procedure you already did with the 3 smaller pieces, but don't remove the protective sheet yet. This will be done later, when installing the module in the aluminum case bottom.

3.5 Assemble the Main Board into the aluminum case bottom

1. Take the main board from its case.

2. Look for the SD-card holder cover in the wiring bag. This little piece of plastic is just to make sure you can't accidentally push the SD card into the gap between its slot and the case, thus losing it. But ... can this happen? Well, it's not easy, but we provide this nice piece of plastic for a reason ;-)

3. Plug the SD-card holder cover on top the SD-card holder. Please, put attention to the orientation. The tiny plastic feet must get inside the 2 corresponding tiny holes, then push slowly until it's totally inserted. It should get clipped. Once it's inserted, don't try to remove it or you probably would break the little plastic feet. This is a one-time operation.

4. Take 4 x ISO7380 M2.5 screws. They are the smaller ones with rounded head.

5. Plug the RBPi5 (with the thermal block attached) on the Main Board's RBPi socket, the big one with 2 rows of 20 pin-holes each. Pay attention to not bend any pins. Also note how the display flat cable should go out from the RPi5, as seen in the photos (zoom in if you have doubts).

6. Fix the thermal block to the main board from the backside using the 4 x M2.5 screws.

Note:

At this point, it's recommended to do steps 3.6 and 3.7 in advance. Most people find more comfortable to plug the SD-card & USB-C adaptors before assembling the main board in the aluminum case. Up to you!

7. Take 7 x ISO7380 M3 screws. They are the mid-size ones with rounded head.

8. Remove the protective sheet from the piece of thermal pad stuck to the thermal block bottom and softly place the main board in the aluminum case bottom. You will find it more comfortable to grab the thermal block to do this operation. Fix it using the 7 x ISO7380 M3 screws. Please, note that the mainboard have some spare mounting holes that are not used with the V5 alucase. You could easily guess the right mounting holes because they should match the 7 alucase's mounting stands.

3.6 Plug SD-card adapter

1. Look for the SD-card adapter in the wiring bag.

2. Carefully, using 2 fingers, one on each hand, pull the main board's SD-card connector tongue until it's totally open.

3. Insert the SD-card adapter's ribbon cable. It must be inserted straight, with the metal contacts side facing up.

4. When it's totally inserted, push the tongue with 2 fingers at once and close the connector. Pay attention to ensure the cable does not move out of the connector. If it's not fully inserted or not straight enough, repeat the operation until it's OK.

5. Plug the SD-card adapter into the RPI5's SD-card holder. The connector is rotated 90º respect to the cable, so you must softly bend the ribbon cable to get it plugged-in. Check the pictures and proceed slowly, always using the minimum amount of force. Don't force the cable, bend it softly, please.

THIS IS A CRITICAL STEP to get the main board SD-card slot working right. Extreme your care because the SD-card adapter's cable is delicate and easy to damage, specially the join between the flat cable and the SD-card plug.

3.7 Plug USB-C adapter

1. Look for the USB-C adapter in the wiring bag.

2. Carefully, using 2 fingers, one on each hand, pull the main board's USB-C connector tongue until it's totally open.

3. Insert the USB-C adapter's ribbon cable. It must be inserted straight, with the metal contacts side facing up.

4. When it's totally inserted, push the tongue with 2 fingers at once and close the connector. Pay attention to ensure the cable does not move out of the connector. If it's not well inserted or not straight, repeat the operation until it's OK.

5. Plug the USB-C connector into the RPi5's USB-C socket.

3.8 Secure the thermal block to the aluminum case bottom

1. Look for 2 x DIN7991 M3 screws. They have countersunk flat heads.

2. Flip the aluminum case bottom and look for the 2 countersunk holes. Using the Allen wrench, punch the thermal pad through the holes.

3. Screw the 2 bolts and tighten them well enough, but not too much.

4 TOP PART

4.1 Secure the top-spacers on the control board

1. Take the control board from its case. You don't need the silicone buttons yet.

2. Take the 8 x brass spacers 10mm and 8 x ISO7380 M3 screws (the mid-size ones with round head).

3. Secure the 8 x spacers on the control board's top side. To do this, insert the bolt from the back side and while holding it with your finger, fasten the spacer with the other hand until it's tight. You don't need a wrench for this, but you can use one if you like.

4.2 Assemble the display on the control board

1. Take the display from its case. Don't remove the protective sheet yet. Flip the display and remove the 4 yellow protective sheets from the outer spacers. You can use your fingernail or a cutter for this operation.

2. Take 4 x ISO7380 M2.5 screws (the smaller ones with round heads).

3. Secure the display to the control board's top side using the 4 x small M2.5 screws. Don't tighten these bolts yet!!! The display must be loose to get a good fit with the aluminum case top part. You will tighten these screws later. Pay attention to the display orientation. The display FPC connector for the flat cable must be accessible through the main board's square hole.

4.3 Plug the flat ribbon cable into the control board

1. Look for the control flat ribbon cable in the wiring bag. It's 15cm long and 1cm wide. Contacts are crossed, with one side faced up and the other side faced down. Be warned that your cable color could be different than those shown in the pictures. It could be grey with blue tips or black with black tips. If it's black, do not confuse this cable with display cable!

2. Carefully, using 2 fingers, one on each hand, pull the control board's FPC connector tongue until it's totally open.

Note:

Please, note that the white JST connector shown on the pictures at left may not be soldered in you control board. Don't worry about it as it's not need it for normal operation.

3. Insert the ribbon cable into the FPC connector. It must be inserted straight, with the metal contacts side facing up. This cable is reversible, so you can take any of the 2 caps, while taking care of placing the metal contacts side facing up.

4. When it's totally inserted, push the tongue with 2 fingers at once and close the connector. Pay attention to ensure the cable does not move out of the connector. If it's not well inserted or not straight, repeat the operation until it's OK.

4.4 Secure the control board, silicone buttons and display to the aluminum case top

1. Look for the aluminum case top part.

2. Look for 8 x DIN7991 M3 screws. They have countersunk flat heads.

3. Place the silicone button pad on top the control board. Note the tiny silicone studs in the bottom of the pad and pay attention to make them fit into the small positioning holes on the control board. Once it's done, softly push the button pad to the side to check whether it sits snug in it's place. The pad shouldn't move when you try pushing it to the side.

4. Use the "Screens & Bits" case as a mounting stand and place the control board on it, as shown in the picture.

5. Place the aluminum case top part over the control board taking care of orientation and proceeding slowly. It's a good time to remove the display's protective sheet, or at least, fold the green tab out of the way so the display makes a good fit into the case's window.

6. Secure the control board with the 8 x M3 countersunk screws. Again, tighten enough, but not too much.

7. Flip the top part and place it over the carton-stand again. Now is the right moment to tight the 4 display screws from step 4.2 (do you remember?).

8. Congratulations! We are ready to join everything together.

5 JOINING BOTH PARTS AND CLOSING THE CASE

If you want to place a CR2032 lithium battery for the RTC (Real Time Clock), this is a good moment. If not, don't worry, you can open the case and do it later.

5.1 Plug the display flat cable into the display

1. Take the cardboard box labeled as V5, which contained the aluminum case. We will use it as a mounting tool in this step. Place it at right side of the zynthian's bottom part forming a 90º angle, as shown in the picture.

2. Place over the box the zynthian's top part, with the display surface touching the cardboard and the display connector at left. Just like shown in the picture.

3. Using two fingers, one on each hand, softly pull the display's connector tongue until it's open. Insert the flat ribbon cable coming from the RPi5 into it so the black side is face down and the copper contacts face up.

4. When it's totally inserted, softly push the tongue using 2 fingers, one on each hand, until it's totally closed. Pay attention to ensure the cable does not move out of the connector. If it's not well inserted or not straight, repeat the operation until it's OK.

Note:

Probably you are thinking that we could use longer cables so these final steps would be easier. And you are right, it would be easier to assemble, but the resulting device wouldn't be so good. Longer cables means more EMI (Electro-Magnetic Interference). The DSI signal coming out the RPi is specially noisy and although the DSI cable we use already include some EMI shielding, the audio circuitry is close, just a few centimeters, and we prefer to reduce EMI to the minimum. Think that you assemble your zynthian once, but you (hopefully!) will use it for years and i'm pretty sure you want the highest quality of sound, so it's worth the extra effort to connect shorter cables.

5.2 Plug the control flat cable into the main board

1. Relocate the zynthian's top part so it's partially fitted with the bottom part, forming a 90º angle. Please, move it slowly and take special care of not forcing the display cable that you just connected in the step above. You can remove the cardboard box as it's not longer needed.

2. Using two fingers, one on each hand, softly pull the main board's control-1 connector tongue until it's open. Insert the flat ribbon cable coming from the control board (top part). Do it straight, without bending or twisting it in any way, so the metal contacts side is facing up.

3. When it's totally inserted, softly push the tongue using 2 fingers, one on each hand, until it's totally closed. Pay attention to ensure the cable does not move out of the connector. If it's not well inserted or not straight, repeat the operation until it's OK.

5.3 Close the aluminum case

1. Without moving the parts from the last position, you are ready to close the case. Now you are really close to finish the assembling process!

2. Close the case slowly, taking care that the cables are not being trapped. Probably you would need to help the control flat cable to get into the case while closing it.

First boot splash screen

3. Before securing the case top and inserting the knobs, it's a good time to burn a SD-card with the latest zynthian software image and check everything is working OK. Please, use a good quality SD-card and follow the instructions carefully.

First boot could take some time. After a minute or so, you will see the display fill with upside-down text, then a login prompt, which will automatically continue. Don't be impatient - wait perhaps 5 minutes until you see the splash screen with the logo. If the display remains black after 1 minute (no upside-down text is displayed), please re-check the instructions and re-burn the SD-card again. If this still doesn't work, try with a different SD-card before reporting in the forum. For solving SD-card issues, it could be useful to check the RPi5 status LEDs.

Once you see the splash screen, it could take a few more minutes until the system is ready. You deserve a beer, or at least some some tea or coffee. When the first-boot process finishes, the Zynthian will reboot and you will be in the main menu, ready to play.

5. If everything worked fine and your zynthian is alive, please, finish the task before start exploring your new zynthian V5.1. Take the remaining 6 x ISO7380 M3 screws and secure the case, 3 on each side. You should place all the 6 screws before tightening any of them. Tighten enough, but not too much.

5.4 Attach and secure the knobs

1. Take the 4 x mechanized aluminum knobs from the wiring bag and the 4 x super-tiny DIN916 M3 screws (headless screws).

2. Insert the headless screw in the allen wrench and screw it partially into the knob side hole, until its head is slightly over the knob side.

3. Repeat the step for the 4 knobs.

4. Turn the 4 x rotary encoders until the flat cotter is pointing outside.

5. Tighten the headless screws. Enough but not too much.

6. Congratulations! Your Zynthian V5.1 is ready to boot for the first (or second??) time. If you didn't yet, it's time to burn a SD-card with the latest zynthian software image. Please, use a good quality SD-card and follow the instructions carefully.

Note that the wiring kit should include a little tool to help inserting/removing the SD-card. It's a small rectangular piece of black-anodized aluminum with the zynthian logo, like shown in the picture:

6 First Boot

First boot could take some time. Don't be impatient and wait until you see the splash screen with the logo. If the display remains black after 1 minute, please, re-check the instructions and re-burn the SD-card again. If this still don't work, try with a different SD-card before reporting in the forum. For solving SD-card issues, it could be useful to check the RPi5 status LEDs.

Once you see the splash screen, it could 1-2 minutes to finish the configuration process. You deserve a beer (hey!! don't abuse if you already took one!!), or at less some tea or coffee. When the first-boot process finishes, the zynthian will reboot and you will be in the main menu, ready to play.

It's time to remove the display's protective sheet (please, do it!!) and take a look to the user's guide!

If the first boot did not finish right and you did not get into the zynthian user interface, you should carefully re-check the wiring before trying again:

• If the display remains black, you should check the display cable connection.
• If you get the ERROR screen, most probably your control board is not being detected and you should check the control-1 cable connection.

You should check both sides of connection. Check that orientation is correct, the cable is well inserted and the connector totally closed. If it still doesn't work, you could look for damaged cable contacts, solder bridges on the PCB connectors, etc.

WARNING!!

AFTER A FAILED FIRST BOOT, YOU SHOULD NOT BOOT AGAIN WITH THE SAME SD-CARD AS IT IS.

If hardware can't be detected, the SD-card is configured as "custom hardware" and first boot is disabled. You must re-burn the SD-card or reset the SD-card from the terminal with this command:

set_first_boot.sh

You can reach the terminal from webconf or using SSH.

From the terminal, you can check the first boot log with this command:

cat /root/first_boot.log

This could help you to understand what is going wrong. You should include this log when asking for help in the forum. Also, when reporting first boot issues, it could be very helpful to include the output of this command:

i2cdetect -y 1 

When everything is OK you should get something like this:

    0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: 20 21 -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- UU -- -- UU -- -- 
50: -- -- UU -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: UU -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --                         

If things are not working OK, you could get something like this, for instance

    0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- 4a -- -- 4d -- -- 
50: -- -- 62 -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: 60 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --                         

Note the absence of the chips addressed in 20 & 21 (2 x MCP23017). This means your control board is not being detected and most probably is not well connected.

7 V5 KITS SOLD BEFORE 2025-06-01 - Fixing FFC connectors

Recently we have detected a little defect (thanks @simmeah!) that could be the cause of some rare issues reported from time to time. We never experienced these issues in any of the builds we realized in zynthian labs and this is the reason we haven't detected the problem until now.

WARNING!!

All kits sold after 2025-06-01 are fixed and free from this defect.

The symptoms

• Control board connection issues, like:
  • Control board not being detected on first boot (see section 6).
  • Some buttons or knobs behave erratically or don't work.
• SD-card extender doesn't work or it's not stable enough.

and:

• YOU HAVE DOUBLE CHECKED the build tutorial and you are sure you followed the instructions carefully and everything is according to them.
• You are using good quality SD-cards of the right sizes (32 or 64GB). Also, check the SD-card extender is not broken nor damaged.

Note:

This should be a last-resource action before considering to replace the board.

The defect

The FFC connectors soldered on main and control boards doesn't fit perfectly the standard ribbon cables we include in the V5 kit, causing the cable to bent when closing the latch and potentially causing bad contact or, at worst case, damaging the flat cable.

The reason is we accidentally choose a wrong part number and didn't realize until now because the difference is really small and it works most of times. Indeed I never suffered the issue in any build I did here, in zynthian labs, and I did a few!

We have already fixed the BOMs so next boards will be manufactured with the right part number. Also, we are fixing all boards we have stocked so:

Note:

ALL V5 KITS SOLD AFTER 2025-06-01 ARE FREE FROM THIS DEFECT and you don't need to fix this because we already did. If you have issues, the cause is not this.

The fix

Anyway i would like to offer a solution for those having issues with this. Indeed, the solution is simple and it has been already explained by @simmeah in the forum:

Use a cutter or scalpel to cut the 2 tiny plastic bumps that cause the issue.

The bumps are really tiny and you probably need good eyes or magnifying glasses. The tool must be well sharpened, so the plastic bumps can be cut will minimal force. Be extremely careful to not worsen things by breaking the FFC's latch.

You must repeat the operation for all FFC connectors used by V5. They are:

• Main Board
  • CONTROL-1
  • USB-C1
  • SDCARD-RBPi1

• Control Board
  • CONTROL-1

May the force be with you and remember: better asking than crying!!