Might be the reset circuit. What happens when you power the cab off then on again quickly?
It might be sensitive to your cabs' PSUs, if it's working on Ken's bench.
The only difference betwwen USA and JPN Daioh is a jumper. Bridge JP6 and it becomes Japanese:
If you add a header, then you can have both JPN and USA in one :thumbup:
Sorry man. Usually there are 4 or 5 extra. I will have to ship everyone else's order first, then I will message you with any spares. I think you might be in luck.
I'll keep you posted!