The same thing happened with my 930 SPX. Sent it back to Mossberg and it happened once after it came back, but I haven't shot it enough since to say whether that was a fluke and the problem has gone away.
So, I got a JM 930. The bolt would bind on the shell carrier if minimal pressure was used on the release (no shells in the gun). Also failures to fire with primer strikes but no bangs. Back to Mossberg. They fixed the bolt problem, but now the carrier is cocked and feeds shells diagonally and stuffs them into the side of the chamber as they try to feed, creating a stoppage. I shot ~50 rds. with no failures to fire, but they only seem to happen in matches, so until I get through a match without one, I'm not gonna say it's fixed.
I will say that I have had good experiences with Mossberg's CS and hope that I can get these problems sorted out.
However, I do have a 930 SPX and a JM 930, which if sold may buy me a shotgun that works.