Do you have the original wiring in the cab, i.e. the individual connectors that plug into the board? The soldering on the edge connector and that jamma fingerboard look questionable at best. It could be the cause of the problems.
I didn't realize you were also the poster in the hardware thread. To be honest, you will probably get better help on KLOV. More hardware guys on that forum, and lots of nintendo and DK hardware gurus.
And just to be clear, that japanese code is not unofficial. It's the japanese rom set, and I think with only 1981 Nintendo, is probably the ladder cheat code, but somebody may know better about japan pcb and code variants.