I would take it to a professional gunsmith. He'll probably charge - maybe not if it's the store you bought it at - but he'll probably also be able to explain and show you exactly what happened or tell you if it's a lemon. Plus, if he breaks it trying to fix it, it's his fault.
If you just bought the Mossberg and followed the directions in the instruction manual to manage that, you may be one of the lucky winners of the mass production lottery.