This is the first time I have ever come across this problem. I was building a Colt 1911A1 for my son and after scavaging parts from every drawer and tool box I had enough to build a frankenstein 45 auto. I got it all together and the hammer/disconnect/sear group would not function. I traded different springs, sears hammers, disconnects etc trying to make the darn thing work. Nothing I did helped. Finally I got out a magnifying glass and went over every part in the "firing " group. You are not going to believe what I found. The grip safety had the arm broken off. Yeah. The break was so clean and straight I didn't see it until I turn up the magnification. Without the grip safety working nothing else would work. That was a real surprise as the grip safety is a big steel part and has vertually no stress on it. How it got broken is a puzzle to me. I ordered a couple more from gun parts corp.
Now that is a first that I will store in the back of the old brain pan.
Sarge