I bought a Gen 3 19 two years ago, I was having the same issue but also with really bad ejection patterns. Like hitting me in the face every other shot bad. Anyways I trouble shot through magazines, recoil spring, etc. Turns out that Glock accidentally installed a .40 SW ejector instead of the 9mm ejector. the small difference in where it was hitting the case was causing both malfunctions. I made the swap myself, it is easy and way cheaper($6.99 part) than sending it back to Glock. Check yours out, ya never know? Also mine was made in USA, not sure if that was contributor or not.