Rene, stuff like that is hard to diagnose without having the pistol in hand. Clean it and lube it good and see how it does on the next trip to the range and let me know. Usually, slide lock issues are one of two things, either the contour of the tab on the slide lock that catches on the mag follower or the mag follower itself. If the lower barrel lug is fit really snug to the slide lock pin at lockup it might cause issues, but that usually works itself out after a few hundred rounds. If you still have problems make a note of which mags are in the gun and if the same mag does the same thing or if the problem happens with random mags. We will get it sorted out! <thumbsup>