Get one of the cases that won't fit and go over the entire case with a Sharpe marker. Push it in the case gauge to see where it is rubbing.
Also, knock one back apart that doesn't fit and Mic the bullet just to be sure.
You said your cases plunk after resizing, that means the resizing die is doing it's job.
Also applied a heavier crimp
I'm wondering if your crimping to heavily already. You should only be crimping enough to straighten the flare of the case back out. The crimp doesn't hold the bullet in the case with a 9mm, it only straightens out the flare so it will pass the plunk test or the gauge test if your using one.
Like everyone else here says, the neck tension holds the bullet when dealing with cases that headspace on the mouth of the case instead of the rim, or shoulder.
If you have the die down to far you could be bulging the case at the bullet and belling it out.
Back the crimp die off until you can feel the flare on the case after the bullet is seated then start bringing it down until the flare disappears, you can check this by dragging the jaws of your dial calipers up the case where the bullets seated and when it comes off the case you won't see the dial or numbers jump up.
Something else, when you set up your seat/crimp die, use the shortest case you can find. Then all the rest will be taper crimped properly.