You mention AF, so do you mean security forces? Then, is this occurring when using pool guns or their individual, during CATM events or unit sustainment fire? That info adds perspective.
Sights loose/falling off is normal. Instructors should have a torx driver and threadlocker nearby. Doesn't repeat once installed correctly and not an issue when all the guns eventually get touched.
Suspicious of frame fracture, depending on the details above.
M17/18 reliability is good with mil ammo, and the folks you appear to be talking about typically use a lot of Mk254 and some M882. It works.
I'm no fan of the 320-type, but M17/18 > P320 and there's a measure of fairness here.
I wonder what the high-time M17/18 in that unit is.