Just adding my .02, though it probably ain't worth that much. From personal experience...We were shooting 3 weeks ago. My buddy had a new Head Down Mk12 Provectus. His was doing the same thing. First shot bang, ejects, loads second round and then nothing with a lightly dimpled primer.
I read where it's been isolated to the lower, and gas problem has been ruled out. I'm just relaying my own experience on a very similar situation.
We swapped Swapped BCG's, same result. Dropped in a heavier buffer, same result. I then noticed his lower receiver was dented above the buffer tube. This shouldn't happen, especially on a new gun with 2 mags thru it. So I assumed it was over gassed as the bcg was slamming into the rear of the receiver. Put my upper (home built) on his lower because I wasn't gonna take the chance of doing the same thing to my receiver. My upper operated perfectly on his lower. He took it to Head Down, they confirmed it was in fact an over gas issue. They were replacing the lower and were fixing the over gas issue. He said adding an adjustable gas block. I would have requested a new barrel. Anyway, haven't fired it since.
I read where it's been isolated to the lower, and gas problem has been ruled out. I'm just relaying my own experience on a very similar situation.
We swapped Swapped BCG's, same result. Dropped in a heavier buffer, same result. I then noticed his lower receiver was dented above the buffer tube. This shouldn't happen, especially on a new gun with 2 mags thru it. So I assumed it was over gassed as the bcg was slamming into the rear of the receiver. Put my upper (home built) on his lower because I wasn't gonna take the chance of doing the same thing to my receiver. My upper operated perfectly on his lower. He took it to Head Down, they confirmed it was in fact an over gas issue. They were replacing the lower and were fixing the over gas issue. He said adding an adjustable gas block. I would have requested a new barrel. Anyway, haven't fired it since.