Tacfire 308 - TacFire DPMS .308 Winchester Complete Upper Assembly

Well I have not had luck with mine. I checked it out before installing on my Aero lower and went to the range and fired it with a full mag, it shot and ejected the casing but didn’t pick up the second round. So I took another mag loaded two rounds and fired it and still the same issue. I fired the second round and it wouldn’t lock the bolt back. So far I’ve changed buffer springs and adjusted the gas block and even shortened the buffer spring and still not operating correctly. I’ve done everything I know to do but take it to a gunsmith. I rated it 3 stars given you can’t get a complete upper this cheap and firing it 1 round at a time at 100yrds it’s holding solid 1/4in groups.