Hard stoppage - Del-Ton Pre-Ban M4 Carbine Rifle Kit

Assembled the lower and slapped some sights on the upper, lubed her up and gave a nice function check. Everything seemed fine running until about 40 rounds in. Hard stop. Failed to fully unlock; a bad one. Almost like the bolt face expanded or morphed in the barrel. Same ammo i shoot out of all my cheap builds runs for them all day no problem.
Since the gun was assembled and fired I would have to go through a factory warranty for anything.
I guess this time I “got what I paid for”