MW, two things I can think of.
First, is the brass adequately lubed? Especially the neck area? I've seen expander balls grab and pull the brass as they are removed if not enough lube is present.
Second, I know you said the dies were adjusted properly. But the #1 reason I've found for this to happen is when the die is not seated as far down as it needs to be. Such as when your trying to bump the shoulder only 2 or 3 thousandths. What happens (especially with mixed head stamps) is that the die does not come down far enough to contact the shoulder adequately and yet the rest of the die is squeezing the brass in other areas, so it flows upward.
ETA: I would try adjusting the die so that the press handle just barely cams over (if it's a single stage). Or just give it another 1/2 turn in at a time if your using a progressive.
And the reasons I mentioned mixed head stamps is that (just as an example), you might set the die up to bump Lake City brass 2 thousandths at the shoulder, and all of the sudden Winchester or Remington brass is not even having it's shoulder touched, this is due to the different thicknesses of brass and how it responds to the sizing operation. Also if some of your brass has been shot more than other pieces, it could be a bit more work hardened and not respond to the die as well.
