I'm working on putting a WPC-95 machine back together and two of the pop bumpers are not behaving. In coil test, they fire but then the pops are stuck in the down position. The problem is mechanical, since I can kill the power and the bumpers stay down and a gentle touch on either bumper (with power off or on) causes them to return to the normal position. I've examined them pretty thoroughly and I can't seem to find anything rubbing or binding.
The bumpers were completely cleaned/rebuild during the teardown, so switches are gapped properly and centered properly, and no flattened plunger/stop or bad sleeves here. I understand that parts can get magnetized, as discussed in this similar post from a couple years ago https://pinside.com/pinball/forum/topic/sticking-pop-bumpers. What I'm wondering is whether that could still be the case here given that I've held very small screws, washers, etc by both the coil stop and the plunger and neither seem to show any magnetic attraction. I have the driver board out now and am waiting on some replacement electronics, so I can't easily test solutions but wanted to see if there were any thoughts so that if I do have to order some new plungers or whatever I can do it now rather than waiting.
Thanks for any experience you can share.
Kyle