JAP games don't work? I could understand the white screen on the USA side (no Pin 29 grounding), but not on the JAP side.
If USA cards work, the switch HAS to be wired correctly...right? All the switch does is switch the lines back and forth...if a line is out of whack, the whole thing wouldn't work...
There's some bit of information missing here, methinks...sounds like a PCB job with something amiss, I don't think 8PDT is available in a push-button...let's see a pic!!!