Like the post says, not quite sure what is causing the trouble. Neither will the high score reset button work. Loose connection, perhaps?

I shall look at that tomorrow. Both buttons do nothing, and did work not long ago.

SO, I finally got to it, and the boards had been serviced by barakandl, who is AWESOME--needless to say no cracked solder joints. I have not replaced all the plugs, which I will do soon. After wiggling them, nothing. I looked in the coin door, and followed the Yellow/Red wire, up to the cabinet plug and there was a pile of electrical tape around the wire and a funny additional wire going to the braided ground.
Removed the tape and WOW lots of exposed wire joints. I quickly soldered them, and the coin door test and reset switches are fine.

Now, why was that ground added to the Y/R wire (which is cut excruciatingly close to the plug)? Is this normal? Seems like a hack. Truly.
Should I remove it and trace the problem, or leave well enough alone?

Thanks, dothedoo. I will deal with that properly Wednesday night. Nice game collection!