I took out my 45 out to the range a couple of weeks ago and after about 150rds or so on the last round, the slide did not lock back. I pressed the mag release and the mag would not drop out. I pressed it again and was able to pull the mag out. I set that mag out to the side and used the other mags and the problem didn't happen with them. I inserted the initial mag back in and the slide would not stay locked back. I came home cleaned and lubed the gun, cycled all three mags and it didn't do it any more. Could it have been just dirty? If so why only with one mag? There doesn't seem to be any visual damage to that mag. It looks just like the other two.