Did you replace the battery holder, maybe add a remote holder? If so, can you confirm the battery voltage goes to the chips as previously asked? ( sorry, no schematics to look at right now) I've seen that behavior from a bad throughole at the battery holder on the board and the battery voltage not getting through to the back of the board.

Thank you, Andrew/Barakandl, for explaining what I was trying to poorly say above. I've had that issue on System 6 boards, because of that exact top right battery holder ground connection. I wasn't sure if it was the same for System 7 but I figured it was worth throwing out there.