So the 100 point score reel ends up at 1 regardless of what value it was at before reset? I think this game resets all of player 1's score reels first, then the Player Unit advances and it resets all of player 2's score reels. Does player 1's score change (from 000 to 100) while player 2's score reels are resetting?
There are two circuits that can drive the player 1 100 point score reel. One is through the Runout switch on the score reel that opens when the score reel shows 0 and prevents any more pulses from reaching the score reel coil. The other is through a switch on the M/100 point relay. If you block the M relay switch (orange-red wire to white-black wire) does the problem change?