So, I was shooting an IDPA classier and all my hits were way left of aim. Long story short, my rear sights had shifted.
I loosened the set screw and I was gonna use a brass punch to push the sights back to center. I realized I could easily move the rear sights with just my fingers. Are the rear sights normally that loose? Did I get a good wonky slide?
The pistol has been fine otherwise. No other issues.

The M&P rear sight is not an interference fit like many dovetail, drift-adjustable sights. Hence, the use of the set-screw.

You an use a little blue loctite under the sight and on the set screw if you are worried about it coming loose

^^^^^ what he said. I've had this happen on my 5" 9Pro model M&Ps. During steel challenge matches, no less.

Agreed. Either blue or even green loctite should work.

They made it easy to remove because you have to take it off to replace the block plunger and spring.