The seating die is removing the flare to soon. Open the dies ID. Dont remove the crimp section.
Happened with my .452" bullets.

Or seat & crimp in 2 steps.
The sear die stem needs to be turned all the way down, to seat the bullets.
Then move the seated bullet rounds to the taper crimp die.

I use RCBS dies from the 70s. New dies may have an "M" type expander .