Resurrecting this tread, both for help, and so that anyone with this problem in the future will be able to find one thread with various answers.

I have the same, but intermittent, repeat firing of the small ball in the bagatelle. Have tried both solutions noted above. And multiple other tracings, using paper between switches, etc. Every time I think it is solved, I play a game or two or three and iiittttssss baaaaack. In my case, the one recurring theme is the launch relay sticks on. Manually pull to disengage the relay, and it stops. I have a vague suspicion it is related to the advance unit 10th position switch, but no real proof. Frankly out of ideas otherwise.

Any fresh ideas appreciated.

Bumping and adding, like with one of the posts above. The ball count unit is not moving to the next ball. Tried playing with different springs on the ball count. Even manually moving the plungers to count through all 5 balls. Nothing stopped the small ball from firing repeatedly. Could it be the 10th position on the advance relay, and how do I test that?

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Last post: Found two problems. First, there was some gunk on the switch stack for the small ball rest switch. Turned out it was conductive. Second, the spring on the launch relay latch was weak. Cleaned the gunk, replaced the spring. Fixed.