Hi pomfreta,
Welcome to the forums!
Sorry that your first post here must be such a downer. Not having any replies is not super either, but could mean that no one had such a problem before which is hopeful 
Seeing the picture, you already opened the keyboard. Are you comfortable programming the ATMEGA GD32F303 directly via the Arduino IDE?
I found another topic discussing a similar issue with a Model 01, not sure if it is applicable in your situation.
Did you contact Jesse/Kaia via email?