I worked on a 930 for a friend...not a JM Pro, but I imagine theyre pretty much the same inside with a little exterior branding. Having seen the way they're put together, and the shoddy parts that they used in it from the factory, I wouldnt touch one with a 10 foot pole.
The immediate problem was that the pin that holds the shell catch broke (after putting only a handfull of rounds through it), and the gun stopped feeding. It's a tiny little 1/16" pin, and you can't see it until you get the whole assembly apart, which was a fun trick in itself. IMO the pin is too small for the forces exerted against it, and it doesn't help that Mossberg used a part with shoddy metallurgy as well. I fabricated a new pin from an old drill bit, and it has held up so far but there's no telling what that harder tool steel will do to the cheap components it interacts with over the long term.
The handguard retaining system on those guns leaves a sloppy fit, and some of the plastic parts in the recoil system don't inspire a lot of confidence toward long term durability in the manner that they're employed. I had considered offering to buy the gun off of my friend, but once I got a good look inside that idea vanished. I think I'd rather have one of those cheap Turkish Benelli clones that everybody seems to be selling these days than a 930, and I'm not all that enthusiastic about those.