One of my bulgie maks has failed to lock the slide back when empty; maybe 4-5 times in about 400rds. It's not my mags (same mags have never done it in my other bulgie).
Hasn't done it in the last few hundred rounds, though. I have a spare slide-stop to try, but I'm not going to swap it until/unless it happens again.
These milsurp Maks are very accurate, ultra-reliable pistols. Neither of mine has ever jammed, and they only get fed cheap Barnaul JHP ammo. The $150 price is just icing on the cake.
EDIT: make sure you disassemble and clean the mags; there's alot of cosmo in there that can slow down the follower, which is what engages the slidestop when empty.