I own a handful of the Desantis Nemesis pocket holsters and never once had a issue with any of them. As long as you're using the correct holster for the gun, just because it fits, doesn't necessarily that will work for the gun. You have to match the model gun you have to the description/model on the tag on the plastic bag the holsters are sold in.
With that being said, all I carry are revolvers. 642 has been my EDC. No mag problems here!