Clean the shotgun. That includes the trigger assy, and the recoil spring.
99% of jamming problems are caused by nut behind the stock.
On a hunt to ND there was a bonehead who had a 391 that was constantly jamming. This person was raising 7 kinds of he%%. So much so that the guide, myself and others got pretty mean with him. Later he was asked when was the last time he had cleaned the recoil spring. He said never, then the retard went so far as to say that there was no recoil spring in the stock.
Clean and take care of your equipmet. Lube the rails lightly with Miltec or FP-10. Those that brag about not cleaning are IMO nothing but Lazy.
My SBE II's have been nothing but FLAWLESS.