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.
Yep, they had a short lived affair with the Smith and Wesson. They are having grief with their new Gen 4 Glocks rusting now.