Reloading once-fired brass with sealed primers will get you "ringers" every now and then. The fact that you are getting them with regularity is a bit unusual. It could possibly be a combination of factors that allowed the sealant to migrate completely around the circumference of the primer down to the bottom of the pocket. This effectively glues the primer in place. When you attempt to de-prime, the force of the de-priming pin is great enough to push the anvil through the top of the primer while the sides remained glued in place.
I've had a few ringers, but never enough to try to figure out a fix. My experience was more like: clear the jam, disfigure the case and throw it away, continue reloading.