Im still leaning towards a switch in put issue here.

Could be the female connector thats at fault as then boards would be OK, but not read one of 2 switch closures.

Game scores when drop is down... OK.. that side works OK.

But game either does not read all are down or cannot do anything about it.

The fact that your coin door switches are doing nothing also suggests to me that maybe the 3 drops down is not being read at CPU.

The coin door switches have nothing to do with the driver.. it is straight into CPU, then either out to displays or down interconnector to driver board.

If this were me..  would be following the switch closures to the CPU and then to the first chip inline which im assuming would be some sort of buffer like a 7407. Any voltage spike to this chip would take it out... thats what its designed to do. Had the coil diode been put in the wrong way round.. i would be looking at this buffer chip... maybe coin door switches share same chip?

look at your schematics for GORGAR and see if the coin door test switch AND 3 drop switches are on the same female connector and also  a common IC

Boards tested fine on Williams board tester by Skybeau... we know that these are good then