I don't know about the issues with 9mm in the Gen 4's. It would make sense that they would if they changed the design to accomodate the 40. The Gen 3 9mm ran like a sewing machine. The 40's were the ones with the issues. And then it was only with a flashlight because the frame was flexing enough to cause a stoppage when a light was mounted. Using a less hot round helped.

The Gen 4's we got had bad trigger connectors. The recoil springs were bad and there was a third issue with a part but I don't recall what was replaced during that one because I was out for surgery when evereything was switched out.

We had the later Gen 3's and they were enough to have us switch to the M&P until Glock sweet talked us into using the Gen 4's. Time will tell if the repairs on the gen 4's will make it an acceptable fighting pistol.

My early Gen 3 is great. But I don't use a pistol mounted light.

Don't get me wrong I have been a fan of glock for a while. They just need to get back to what made them great.