OK. When I turn it on, the latching relays latch and the Game Over light comes on. There are credits on the game and the credit light is on. Pushing the start button does nothing. If I manually trip the start relay, the score motor turns, the reels all go to zero and the score motor keeps on turning while the reset relays for Player 1-2 and Player 3-4 chatter endlessly. I would guess this means something is not telling the score motor that the scores have been reset.
I have inspected/cleaned all score reels and found a few loose wires that were then resoldered where they belong. At a bit of a loss as to where to look next and am taking all advice. Will get some video to post after I pause for lunch. Thanks in advance!
PS, Sonic is Williams based if that helps.