Looking at the schematic for this game, there are lots of switches on the switch matrix that use 0.5uf ceramic caps. If you cut a leg off each cap that's attached to a switch, you may find the problem goes away. These caps have a tendency to sometimes short internally when they got bad, which can screw with the switch matrix. They're there to help the mpu detect fast switch closures, so it's recommended to replace them if they're bad.