Have a close look at the coin switches. On those machines, they are always getting mangled and often short against the metal parts. This grounds the switch matrix and causes all sorts of weird behavior. You can set the game to free play by setting the max credits register (18 I think) to zero. This eliminates the need to touch them again.

If you get stuck, I can come to you and repair it. I do this for a living, so rates would apply.

For those interested, I went out and repaired this. There were two problems: a bad Scanbe PIA socket (No such thing as a good Scanbe!) and a pinched wire on the playfield which was shorting two rows together. The upper flipper was sticking on its EOS switch. Cleaning was all that was needed there.

I did the original work on the MPU and changed out the yellow roms to green ones. One thing I hadn't realized was that the adjustment table changed with the green roms. I always thought Flash was Flash, but no, you have to have the correct table for your roms.

The coin switches were fine.