u/AdministrativeCap169

I’m getting some very inconsistent fire with my g19 gen 3. The shell on the left did fire and the shell on the right did not. Any ideas on what it could be? It currently has a Durkin tactical upper on it. I already replaced the firing pin spring and sleeve for oem parts. This is a brand new gun with brand new parts.
Any ideas help because I’m at the point where I’m just going to start replacing stuff with oem parts.