As has been mentioned, the issue has been with the M&P9, Full Size. There haven't been any problems noted with the 40 or 45 cals, but the Full Size 9 is still a crap shoot. Smith has not addressed the real issues with all its lock up and trigger fixes. Some of us think the real issue is that there is less mass on the 9mm slide and the lesser thickness makes it more susceptible to warping than the thicker slides of the 40 and 45, whose thickness is necessary to help control the greater recoil. There may be other problems, but this one hasn't been addressed.
Further, the accuracy issues in M&P full-size 9 don't appear at 7 to 15 yards; for some reason, if they're present, they appear at 25 yards or so. If present, the problem will show you a group of 6- 8 inches from a rest, at 25 yards.