Aha! Lots of guns have problems with Winchester Universals. The steel rims expand and grip the chamber creating excessive drag. I have seen Expresses, Novas, Mossbergs, and even a BPS being beat on the ground to try and eject these. You could try honing the chamber to make sure it is smooth and there is no plastic or other build-up at all. Easiest route is to use different shells. My 1100s will cycle them, but the rip the heck out of a lot of the shell bases doing it.
What could have happened... did.