Quoted from Betelgeuse:I have this same issue. There's a sweet spot where the ball can just rest right against the left edge of the bottom pop bumper from time to time. I can always Nudge it out or wait for a ball search, but I think a different post right there or even a different rubber ring would resolve the issue. It's in a tough spot to get to though
Star Trek pro has this same issue, it was in a spot you can't see so i fixed it by hot glue gunning a very small, torn off rounded piece of packing peanut (thanks pinball life) right in that spot. No more stuck balls. It's bouncy so the ball keeps moving you'd never notice it was there.