Only Vol+ not responding

[nothor]

I bought a V1 Switch (from 2017) and the Vol+ was not working (Vol- and Power was OK).
This is a problem, because I want to softmod it
I thought it has something to do with the flex cable and I replaced it (twice!)
After reboot and inspecting the circuit I have no clue where the problem could be.

Things I have done so far.
- Reboot Switch (several times)
- Update Switch to 21.1.1
- Change volume via SW (it works)
- Try entering Recovery (Power + Vol+) --> NOK
- Check Resistance directly from flex cable connector (0 Ohms by pressing, 10'57kOhms open)

Attached some photos of the circuit, if you see something strange or you have a recommendation to check something.
Marked in red what I suppose the Vol+ circuit goes.

 

[thesjaakspoiler]

If the vol - button gives the same readings when the ribbon is connected to the main board, then you can conclude that your ribbon is fine.
Then your issue is on the main board.You could try soldering a wire to the resistor in picture 2 and see if the Switch responds to pulling it to GND.
In the past I have seen some posts about missing resistors or damaged traces causing the behavior you describe.

Maybe also take a look at the connector.
You never know whether the previous owner damaged or bend some of the pins.