Hello 4Max. I had a Williams Expo that had a score motor that over-ran home position. The gears would keep turning AFTER the motor stopped. I took enough of the score motor assembly apart to get to the motor gears. I thoroughly cleaned the gears and axles and then put on some Super Lube. I don't know if this is "accepted" or "best" policy for score motor maintenance but it stopped the cams over-runing the home position.

Check the motor run switch. It's on the schematic in section A-14 on the index cam. It's that switch that tells the motor its rotated a complete cycle.

I'm think that the run SW on the score motor is at fault, make sure it is closed until the cycle is complete. odd that you only see this happening on player two.

Hi 4Max +
I agree with chris (post-4) - The Score-Motor-Switch "B" on the Index-Wheel. Whenever You check a Switch: Not only look at the blades / contact-points - ALSO grab the wires (soldered-on) and gently pull. Wires can be broken-off - they are stiff and stay in place - then a bit of vibration / shaking -> the wire moves (no contact) - another bit of vibration / shaking -> the wire moves back (contact again).
The strange thing is: It does not happen at player-1, strange.
ipdb.org has a schema in three parts: http://www.ipdb.org/machine.cgi?id=649 -> might want to (?) make a copy (down) onto Your computer ("righthand-side" Mouse-click -> save target as) -> Do You see at schema (first part), 4-C the "Score-Motor-Switch-Index-B" ? Wires "Yellow" and "Orange-Green" ? (See in Schema second part: "Drawing of Score-Motor"). Greetings Rolf

P.S.: Strange, when I make a copy of the schema (onto my computer): My copy is turned clockwise (90 degrees) - And: I can open my copy with "MS-Paint" and therefore can comfortably move around in the schema.

Great news! Thanks for letting us know that you got it working.

Not if you want your EM to work the best it can. You will be rewarded for your patience and hard work.