Stevens 320 shotgun issues

Bought the Stevens model 320 home defense shotgun. Lately I've been having serious issues with the shells following each other as I pump to reload. I'm clearly not a gunsmith and have a general knowledge of weapons. I'm guessing that whatever mechanism that is supposed to catch the next shell isn't working. Nearly every time I cycle the pump (to eject the spent shell and load a new shell) the new shell is immediately followed by the next new shell from the tube, jamming both inside. I've done multiple searches and haven't found anyone else with this problem. My dad has the exact same shotgun and his works just fine, haven't had any issues with his after about 100 shells. Just curious if any gun-geniuses out there can tell me if this is an easy fix, if I should send it in to Savage or just run it to a gunsmith. Thanks for your time.

believe it or not, i have about 500rds through my 320 with zero issues..its been a very good shotgun..sorry to hear your having an issue, lets hope its isolated..