I am rehabbing a Target Alpha (Gottlieb 70's EM) and the metal rings on my pop bumpers randomly stick in the energized position after either of the bumpers is triggered. I've checked both switches on both bumpers - neither are sticking closed. I've checked the switches on the related scoring relay - gapped correctly and cleaned, not sticking. The action on the metal rings is smooth when operated manually - there doesn't seem to be any mechanical issue. The rings, skirts, plastic housing on each bumper is all new. When they stick, I can manually (with some effort) unstick them but it's as if the coil is still magnetized or something. There is resistance.

What could cause this behavior? Is there a specific gap on the switches that I should be adhering to?

Thanks

Yes and yes

Noticed that the stuck rings release when I press my flippers.