There's a schematic on ipdb.org:
There are nine different normally open switches that connect to the orange-green wire that sends power to the Score Motor. Any one of those switches being closed or shorted could cause the motor to run. Check each one visually to see if you can tell which ones are closed. If that doesn't help block the switches with paper to see which ones when blocked will let the motor stop. One of the nine switches could be the problem or it could be the relay that's closing the switch that is the problem. Either way you need to figure out which switch is closed.