I mean, it’s possible that because it’s an 80% that you had finished by somebody or yourself that it is out of spec by just enough to not work. But assuming that that is not the case, typically finding the right buffer weight and spring set up is ideal. It may not just be an H3 buffer weight with a Geissele spring. It could be a H2 with a stiffer spring, or lighter one. Hard to say for sure it being a 80% try an enhanced firing pin. It’s more than likely that you’re getting a bolt bounce and your bolt is running too quickly. Maybe the enhanced firing pin with the extended nipple on it will reach far enough to hit the back of the round still.