Sounds like it may be a memory or CPU issue?

Sound and switches work OK in test modes?

I don't have the manual, how many optos does this game use?

Check the opto's in front of the cabinet.
There are 2 in front of the cabinet.
One close to it and one upon entering the space in front of the cabinet.
One side should light up red and the other is the receiver.
The other opto is mounted in reverse.

+1

I had this issue as well. It was working great when I bought it but acted up when I got it home. I cleaned the optos in front of the file cab with a q-tip and some cleaner and it fixed the problem.
I am thinking the bumpy transport home either got the opto misaligned or bumped up some dust that got the optos all dirty.

Those opto boards also suffer from cold solder joints. Our was doing the same thing and that's all it was.

Good luck.

Was this ever fixed? I need closure!