On the score unit stepper for the units ("ones") score position, there is a semi-circular wiper located just behind the metal score reel, held down by the same three screws that hold the metal score reel to the spindle. This wiper has a contact that touches one of ten rivets to complete the match circuit. It could be that this wiper has been put in the wrong position on the spindle, and that is causing the contact on the wiper to be out of sync with the current number on the reel.

If this is only happening on one of the players, and the other player match is working correctly, check to see if the wiper position on the faulting unit is different from the working unit. If so, move the wiper on the faulting unit so that it matches the wiper position of the working unit, and that should clear up the problem.

- TimMe