mk9 slide won't stay back on one mag

[Tpsfoto]

Hi all,

I have one mag that causes the slide not to stay back after last round.
it is a 6 round mag and visually everything looks correct. I even cleaned it completely prior to shooting.
any clues? MK9

thanks!
larry

[kerby9mm]

Does the slide stay back when you operate the gun empty? Does that mag have the metal tip on it? That's what pushes the ss up after the last round.

[Cokeman]

How old is it?

[FLBri]

If it is consistent to one mag, and one mag only .... you can permanently fix the issue forever for $30.
Throw it out and buy a different one. No muss, no fuss.