For what it's worth, my current count of 10mm M&Ps having problems with the mag drop issue is 27, but I haven't updated this in quite awhile:
S&W M&P 10mm Pistols: Prevalence of the Magazine Drop Malfunction | by Mark | Medium

I hope that S&W has sorted out the problem by now. If they've made changes, I wish they'd be transparent about what changes have been made, and to which guns. I'd like to try the 10mm M&P again, even with my two very negative experiences. It's hard to bring myself to do that without knowing which pistols are good to go, though.

In the meantime, my Sig XTen has been great. Still, I prefer the M&P platform to the 320 platform.