Not sure when the problem started because I havent shot it in a while. The slide is difficult to pull back and it doesnt go into battery 3/10 times when shooting. I exchanged guide rod/spring with another Glock that was easier to pull back and it didnt resolve the problem. So it is not a spring problem. I installed an ext slide release two weeks ago and read that it could interfere if the spring on it wasnt seated right. So I removed and reinstalled it and it didnt help. I wonder if I damaged the frame or something when installing the slide release initially. The pin was difficult to remove and install. (I didnt know they would only go in and out from a specific direction.) Thus I banged on it the punch with a lot of force until I figured out the right way. Any ideas?