I experienced this same issue and believe it's just that the magazines are made of stamped metal (and they pushed out a lot of them) and they're not super polished on the inside.
Metal on metal; gears need to find a home, mesh.
I was lucky enough to have terrible weather when my M&P5.7 arrived so filling and cycling the magazines before I could get to the range solved the problem for me. When I couldn't wait any more and went to an indoor range, I had them broken in and it ran flawlessly. I fired 200 rounds (100 factory, 100 reloads) that first session. I now have 900 rounds through it (100 factory, 800 reloads) and have only had one failure to fire (no failure to feed) and that was due to the primmer, on a reload.