Gentlemen - we have resolution. glockenturn is the winner; it was residue in the SAFETY PLUNGER HOLE. When I returned the slide, they said it would probably be because of residue. They cleaned it out and ran 30 rounds thru it. Got it back yesterday and had no problems with it today. Also, I want to thank all of you for sharing your thoughts on this problem. It is obvious I have limited knowledge and experience doing this stuff. I have learned a lot from you and especially glockenturm with his advice on how to properly install/remove trigger pins. Thanks.