GTB add-a-ball wedgehead works fine except that it now skips letting me play the last (#1) ball. Once the #2 ball drains, it goes directly into "game over" mode. This only happens when the #2 ball drains. All the other balls subtract one at a time. I manually operated the ball count stepper unit through all 10 ball points, add & subtract, and it works fine mechanically. I have the schematic and I am guessing their might be a poorly gapped or arcing switch in the "subtract ball count unit" circuit that might be sending a prolonged or double pulse, but why would this only happen to the last (#1 ball)? Any ideas or direction would be appreciated. Thanks.

Thanks for the input. There are three switches on that stepper. I cleaned and gapped those before I posted, then checked them again just now. I even changed the fishpaper on the one double switch thinking it might have degraded since 1970. Also checked the wiper plate and disc which I had serviced and they're solid. Everything looks good with that unit. I did just notice a double-kick pulse every time a ball is ejected from the trough, so that's certainly worthy of note and further investigation. All ideas & hints are welcome.

This has been an interesting challenge. The "double-kick" I was hearing at ball launch was the ball eject kicker needing two kicks to get the ball over the inner guide and out into the launch alley. Wear and age had taken its toll. I modified the kicker switch angle and shape to enable the ball to rest in the center of it's kicker cradle and then launch it with the correct trajectory. I've been through this phenomenon with Gottlieb EMs before, but it never affected scoring until this machine. It works great now. Thanks for the attention and advice. Hope this helps someone else with an AAB.