You'll need to check the schematic to see which switches send power to the score motor... Some simple items to check: Do the score reels completely reset to zero after the start relay is activated? Make sure the coin switches are not stuck in the closed position.

Find the score motor icon on the schematic and follow the circuit back to the primary switches that send power to the score motor. For this era of machine, those switches are usually at the following relays: D, J, O, Q, S, U, SB and score motor switch 1C. Most likely, these switches will have a red/white wire attached to one of their wire lugs. Make sure these switches are clean and adjusted properly...