Still got a couple slam tilt switches to check, but I started a game and then unplugged the coin door completely and the problem is still present. I've tested all the diodes related to this part of the matrix and they all test good. So for now, In stumped.now another problem has popped up where all three pop bumpers fire together in play and in solenoid test but I dividually when the transistor tabs are grounded manually. I suspect header pins and connectors between mpu and driver or possibly a PIA. But that issue will get its own thread if I can't solve it... Anyway, thanks for clearing up the Bally switch matrix for me and getting me pointed right, I'll update if I fix it.