mine did or does this as well. are you using reloads? i found that the rounds were not letting the bolt fully close, and i mean you could not really even notice it. if shot you will bend the firing pin. I did. used other ammo and it stopped. i ended up using those rounds in my uzi nwhich could care less.

 

Hmmm... no, I shot Federal 115gr brass case round nose jacket and Wolf 115gr steel case round nose jacket... never had problems with those in any gun before.

 

Try dry firing slow the same way...If the trigger still sticks, you know its not ammo related. Check at the bottom of the trigger to make sure it is not dragging on the bottom of the trigger guard at the rear ( this was an earlier issue ).