Quoted from imharrow:
It sounds like the captive ball switch is either gapped too tight and you are getting phantom hits on flipper presses, or there is a switch matrix issue involving the scoop and the captive ball. I have not tried to debug spike, so I am not going to make assumptions about what could be happening.
Go into switch test and bang on the playfield and see if anything triggers. Try putting the ball in the scoop a bunch and see if the captive ball activates.
I am pretty sure this is a hardware or electronics issue with your machine.
OK, I think we are onto something. Turns out the Captive Ball Switch is always ON. In its normal spring-forward position it is ON, if I push on it lightly half way travel (like 1/16") it goes OFF then back ON again at full travel back. I'm guessing this isn't supposed to be happening.
Bumps of the field are enough to make the captive ball switch go into the off position (half way back). This would explain why I am getting Symmetrical book stacking and Gozer all the time without hitting the captive balls.
In the attached photo that is the status of the captive ball switch without playing or touching anything. Then if I press on the physical switch lightly it goes off and then on again when it touches the connection at the back of the switch.
Before I go tearing things apart ... can you advise how best to go about repairing it? (it is like the switch is making contact in the fully open position as well as closed position)