For those people having issues with the plunge rattling and not making it round the orbit/ramp or getting trapped underneath the pop bumper, I think I've found your problem, by accidentally creating it, then solving it.
I had the playfield up for the first time since playing over 500 games without issue, I just wanted to clean it and give the feed from the gauntlet ramp a little tweak.
When I lifted the playfield I noticed a nut missing from the guide.
So rather than going straight on Pinside to complain of the build quality I fitted a nut and tightened it down.
This now meant that the guide had no side to side play in it, and also inadvertently raised the guide higher further up the playfield.
When I put everything back together and played some games almost half of the balls from the auto plunge rattled and came back down the right orbit.
So I went back under the playfield and removed the nut. In the half dozen or so games I've played since no issues with the ball rattling.
As an aside it also means that there is a little give in the guide meaning that if you shoot the orbit slightly late it doesn't bounce off the guide as much and has more chance of making the shot.
I know some have added a washer under this peg to try and stop and pooling or chipping, in doing so it looks like you've created the problem
At no point has the autoplunge strength been changed from default. In fact I think lowering it much more than what it is would compromise the ability for it to make it all the way round the ramp.
I also slightly adjusted the wire guide from the gauntlet/side ramp and now have a near perfect feed to the flipper every time.
The only 'problem' I now have is the drop from the tower seems to be bouncing away from the flipper a bit more making the Hawkeye shot virtually impossible