Sounds like you've found a soln.
I suspect the rounds were separating the bullet from the case while in the magazine from the recoil of the preceding shots.
Then when one of the loosened/longer than normal rds came up for feeding next, that wasn't about to make it's way up the ramp and into the chamber.
That's what you were looking at lying in the magazine and partially onto the feed ramp.

Ejecting it at that point flips it out of the gun but the bullet simply falls out of the casing as it's only held w/minimum tension on a short portion of the bullet,,if any at all.

Dies, bullets, brass,,they all are made within certain specs.
But if the highs and lows of those specs get mixed just right you can have overly tight conditions where things won't go together.
Or on the other end, loose conditions where things fall together with little tension (in this instance).

Sometimes simply swapping expander plugs around with another set of dies will get you a tighter neck tension you need.
Not flaring the brass quite so dramaticly as you've done can help also in some instances.

The expander plug on one set of dies may be a .000 or a 1/2 .000 smaller or larger than another. Add in a smaller than usual bullet dia or the other way around,,thin or thick brass walls,,you get the idea.


That ring on the taper crimped cases might have disappeared on your latest reloads with the lesser flare to the mouth.
Too much flare to the case and the die has trouble gathering the wide outer dia of the flare and bringing it back in w/o it folding in on itself just a bit.
That small wrinkle or fold shows up as a bright spot near the case mouth and looks like an extra deep crimp. But it's just the bunched up matl (brass) being flattened back down by the die.