Thanks for the video and story of first hand experience, SSGN_Doc. That just reinforces my opinion that they use surplus, scrapped and rejected parts. And it doesn't seem that anyone inspects what goes out the door.
I remember an old review by Patrick Sweeney where he tested a Vulcan AR and part way into the test the carrier key crashed into the gas tube and deformed which locked up the rifle. What happened was the barrel nut was undertorqued and allowed the shooter to twist the rails and bend the gas tube. Other comments pointed out low quality parts of the rifle, too. This was the only negative review I've ever seen Sweeney make on any AR so you know it was bad! Actually at the end he softened it up and said there was a use for the Vulcan as an ultracheap AR that would get a person (who is handy with tools and repairs) in to the AR game - if it would be used only as a range gun
The biggest issue with assembling an AR isn't so much getting the parts together right - it's getting the right parts together. You'll remember the quality of a gun long after you forget how much you paid for it.
US Army 1966-69, VFW Life Member, Retired Geek