I am thoroughly convinced that my Donkey Kong PCB is the Devil. When I got it, it worked fine for a few months and then the sprites went missing. Sprites are the moving graphics, you know the barrels coming at you, Jumpman running. I really wanted to get it fixed so I sent it off to onecircuit.com. This is a guy named Adam that I met on the KLOV forums. His work is very professional and I like that he makes videos of the repairs. I got it back and it worked fine but it started having sound issues so Adam is looking at it free of charge. I highly recommend his work. Board came back and it is fixed.
I think I know what caused this problem. While Installing the High Score Save kit from Braze Technologies I pushed too hard on the PCB. It’s a a good kit, the only thing is that the pins are very very tight when you put it in. Mine was incredibly difficult to get installed. Pressing on the PCB probably made it bend and on a thirty year old board everything is ready to break. So when I got it back I re-installed it but this time I slightly bent the pins inward. I mean slightly as in almost imperceptible, and it went right in without a problem.