JD, earlier you said

The problem persists but also when you turn the machine off and on there are 4 credits in the credit window.

That's coming up in audit mode I think.  Before pulling the boards apart and sending them around the country have you tried new batteries and setting the machine back to factory default. This can be done from the top dip switches on the cpu board.  Do you have the game manual to make sense of all these setting, it's available from ipdb?