I do not have a copy of the schematic.....Williams machines typically have a ball count unit that is normally close to the coin unit. Have you manually operated and cleaned all the units? A very common problem is the grease (that shouldn't be on them!) hardens and freezes the units keeping them from stepping. I would start with manually operating both units to ensure they are stepping. The coin unit and the ball count unit work together in that regard.

The short answer is yes....score motor switches do need to be adjusted/cleaned sometime. I use a dental mirror and a flashlight to try to see the switches. With the game off and unplugged, manually turn the wheels and watch the switch in question if you can. Score motor switches can drive you crazy!!! When ever I have a tough situation I will remove the entire motor board so that I can get on eye level with the switches. It takes a little extra time to do it, but it has also saved me lots of time. One tip......make sure all of the switch stack screws are tight. They will work themselves loose therefore not allowing all the switches to work correctly.

A useful tool in this situation is a jumper wire to eliminate each switch and work your way forward or backwards. Meaning, you could begin by "jumping" across the outhole relay to see what results you get. You can do this by connecting the jumper to the yellow wire feeding the make break switch on the outhole relay then connecting to the red and green (? can't see it well on the schematic) on the extra ball relay. Try it, if it works correctly the problem is with a switch on the outhole relay. If no change then move the jumper from the yellow wire over to the red -white wire on the switch of the ball index relay, this would rule out the ex ball relay and so on....