Until you can have the gun looked at by another smith, or serviced by the one you are waiting on, it might be worth trying another brand of shells; just to see if they are more reliable.
I have seen some very bad batchs of ammo. One box of buckshot I bought was so out of spec that I had trouble forcing a round into the chamber or the magazine. The brass base was not entirely round, and/or some of the bases seemed slightly flared and sharp lipped. They kept catching in the gun and not feeding well at all.
Though if that was your problem, you would have probably noticed it while loading the gun or cycling the first round.
I'm just say that badly out of spec shells do happen.