I have my 625 with a 6.25 lb pull that has been very reliable for the last 10,000 rounds. It has a reduced main spring and is smooth as glass. It just started missing two out of fifty. Strain screw is tight, no binding, single action will fire the misses in double.
Only thing I can figure is that I have been a bit lazy and the last 10 or so times the brass has been reloaded I have not cleaned the primer pockets. I also use just the same brass for the 625. I hand seat fed 150's, the firing pin was an extended one and I cleaned the area were the hammer contacts the frame.
I did the trigger job myself about two years ago, maybe it's time to have Mike work on it. I will do another fifty and clean the primer pockets to see if it will help.