The possum cops here in Kentucky switched from the M&P to the Glocks in .40 a couple of years ago. I overheard a couple of them talking at a shooting range one day, and they were fussing about the M&Ps breakage problems.
They never said WHAT parts were breaking, but that it was a problem they had from the git-go.

You can roll a turd in peanuts, dip it in chocolate, and it still ain't no damn Baby Ruth.