is this another answer???...

https://sigforum.com/eve/forums...0601935/m/3750001943

Bill

it wasn't for me...I need to make a call to Top Gun Supply for a new slide lock...

Bill

I shoot the 226 and 229 and when I had the Hogue rubber grips on, I never had a problem with the slide not locking back.
Switched to "old style" panel grips, and now I have the problem.
Hogue grips have a thicker area just behind the slide lock, so my thumb would rest on that.
Hogue a tad too big, so I am looking at the Hogue rubber without the finger grooves.
Just a thought.

Happened 1 time, pretty sure because I gripped the gun so hard including the slide lock when the last rnd was out it suppressed the lock release. No harm, just remember keep thumb away from the lock.

I did the slide release cut on 3 P320 that were different models and the problem was solved.