Quoted from Aurich:
That's not the issue, you're not actually physically knocking the ball off the magnet with the other ball, you just need to break the opto in front of it to release it. The issue is with the opto. Defective boards, something else, but totally unrelated to the magnet strength.
Yup...you guys are absolutely right. I jumped to a conclusion based on just playing and not digging in. I just did a little glass off checking. This is definitely a weird one as the opto seems 100% in testing and throwing the ball in there by hand seems ok too. I'm wondering if stray light from the playfield is messing with the opto? I've heard of that before. I did notice that one side of the opto is quite far away from the "peek hole" in the ball guide. If light from the playfield is shining in there just right, it could be enough to make the reading unreliable. I don't have time right now, but it would be an interesting experiment to make a little shroud and see how that goes. Could also try remounting the opto closer to the ball guide, but not sure if that's possible/feasible. I've seen both very slow and very fast shots both stick rather than release, but also have seen both of those release it just fine. The intermittent issues are always the worst!