did you ever take the magazines apart & clean them as well? A lot of problems with this pistol has been contributed to a sticky mag follower. with the slide forward insert a empty magazine and watch the slide lock. What does it do? It moves up. The magazine spring applies the tension to the slide lock and if you have a sticky follower or weak spring that may cause the faiulres your describing. I would take the mags apart & with a toothbrush use some gun cleaner & brush the soot off the plastic mag follower and insides of the magazine and wipe dry...