Is there something I'm missing here? I don't read that the OP is having cycling issues, rather that the bolt doesn't lock after the last round. Sounds to me like there is something wrong with the carrier latch. Can you manually lock the bolt back? If not maybe there is some crud in there keeping it from locking back or maybe the latch itself is the problem.
Is it possible that it would be cycling rounds just fine but not have enough oompf to lock the bolt back? Doesn't seem like that would be the case. Have you called Benelli?
"Pain or damage don't end the world. Or despair, or ____ing beatings. The world ends when you're dead. Until then, you got more punishment in store. Stand it like a man.........and give some back."