Slide locked with an empty mag?

Try to change the magazine spring. Perhaps its not stiff enough to push the slide release after the last round.

 

Could be a follower but my money is on the mag spring.

 

I got rid of both of my 10rnd mags. They had the same issue, then I put new springs in and they worked too well or something because after round 1 they would jam every time. Different ammo, different glocks, always a jam.