I don't like the way that sounds...
I sent mine in a while back and turnaround was 3 weeks. 10 weeks is insane! SW must have a lot of problem guns out there.
They've been pushing it with sending guns out that shouldn't leave the factory but they always fixed them quick. Now I'm afraid that system is starting to cave in. The M&P line is flagship in their semi pistol line, they should be able to whip that right out unless things are really mucked up there. I got my Shield back in about a week and a half a year or so ago.
Maybe this is obvious but try removing the mag, and pull the trigger (if there is no round in the chamber...be safe) then hold the gun by the slide with your left hand and hit the back of the grip hard into the 'V' between your fingers and thumb a few times.
I have also, put the Shield and other guns in a padded vise and with a dowel on the slide by the front of the barrel, tapped it a few times. If nothing happens, send it back to the factory.
I've had some problems with reloaded ammo where oversized bullets caused one problem and stupid 'small ball' ammo with a rough coating job getting stuck in the lands with the gun being out of battery by about 1/16: I'm not buying any more of either of those bullets. They jammed all my guns up. This is how I got to be an expert in unlocking guns.

An essential tool. I have a heavy brass rod that I put down the barrel and tink on a bullet with just the inertia of the rod a few times to loosen it up.
PS: check your barrel to see if a bullet hasn't gotten 'pulled' and been left in the barrel.