Either yo need to have it looked at for a mechanical problem...................which I doubt is the case....................... or...................... more likely operator error.
Is yours a 3 1/2" chamber ??
You could be "short shucking" the action. It's not hard to do. The 3 1/2"guns, especially, will eject the spent casing before the pump is completely pulled rearward. If, at that point, you start the pump forward, the gun can and probably will jam.
My 10 gauge has run FLAWLESSLY for over 25 years. But I guarantee that if the next shell fired out of it gets short shucked............................ it'll most likely jam.