What could cause ejection problems in a Browning BPS when shooting 3.5 inch shells?

If the gun is not chambered for the 3.5 inch shells, they will get stuck in the forcing cone.

To the person asking the question you can rest assured that there is a problem with the ejection part of your shotgun ,because I had one that did the same thing and I had to take it to a gunsmith and he had to file down the ejectors,,, I believe that's what he called them.

As for the first answer you couldn`t get a 3.5" shell in the gun without realizing something was wrong.