I just had this same issue and it took me a month to figure it out but here goes...

The switch that’s by itself at the far end of the cam that engaged a slot in the disc is one of the Index switches. That Switch must be perfectly set to open at the end of a rotation. Is that happening or is the cam traveling just a bit too far before it tried to stop? The issue I had was that there was too much play in the many plastic links that make up the cam on that reset motor so at the last switch, there was about a 1/16” of play or slack and a such that index switch at the end ended up rolling into the gap where it opens up ( and the cam should stop) but the cam rolled another couple degrees and the switch edge slides up the backside of the notch and closes again thereby providing power to the cam motor and restarting another rotation - endlessly.