I have an unconfirmed theory that on some MNT Reform motherboards, the pins of the power jack are a bit too long or have too much solder on them, and could touch the pins of a keyswitch on the keyboard if that is pressed strongly (the backs of keyboard and motherboards are facing each other). The power from the power jack would then zap the input of the keyboard MCU for that column, and we need to replace the keyboard MCU.
This is why we now manually clip off those overly long pins from the power input jack and additionally isolate them with tape before shipping. Most of the EU devices that we sent out so far do not have this treatment though.
To my knowledge the issue has happened only once in the field and once in the lab. But to make sure it doesn’t happen by accident on your device, I recommend to shorten (clip off) the 3 pins of the power input jack on the back of the motherboard with side cutting pliers and also put some isolation tape there, just to make sure a short can’t ever happen.