I have a tweaked 1911 that I shoot regularly at matches and the past two weeks I have experienced the same failure; the firing pin stop-plate drops causing the firing pin to remain extruded and the weapon will not close into battery (probably a good thing with the extruded firing pin or I would have an eight shot machine gun). I had to complete each match with a different pistol and that really threw off my groove. I replaced the firing pin spring, thinking it might be a little weak, allowing the firing pin to travel too far forward but that did not help. I just replaced the stop-plate but the new one fits exactly the same as the old one and if I depress the firing pin beyond the depth of the plate, gravity will allow the stop plate to drop. I may be having a head-space issue with the primer strike letting the firing pin travel too far forward or not, it does not seem to be a bad fit and I have swapped firing pins but that did not help either. I am wondering if I should stake the base of the slide to arrest movement or if I should bite the bullet and build another slide (I really like this one)?