No schematic for this machine so working in the dark but this is my problem:

There is a subtract ball relay that appears to be working, I.e clean, gapped correctly, etc. But, when the ball drains, it wont subtract say from 5 to 4 balls. If however, I press and hold the rollover switch in the drain trough it will subtract correctly so it would seem that the relay is not being held enough to complete its cycle. That then suggests that there is a motor switch that needs adjusting to pulse the relay for correct operation. Does anyone know which motor switch I should check please?

Thanks, but I have tried that. It seems that the relay itself just isnt holding long enough to complete the cycle.

There is no motor switch paper on the cabinet unfortunately, or of course I'd have checked it through but the the circuit explanations will do the trick now, thank you all for your time.