Why don't people ever put pics in these?
The one with wear in the upper did, and that was common inside any AR with any mileage on it. lol.....####.
Its like any other trouble shooting, 98% of which has been tried already.
Soak your gun in a good lube, like slip2000 or something, to take lube out of the equation
then;
1) different ammo ( AE seems to cycle well in most guns, and isnt to expensive)
2)different mags ( I know you said you tried 7 pmags. try a steel 5/30 and see)
3)different bolt (you must know someone with a piston bolt!

)
if none of those work, its probably the gas system.
if its #1, some guns just hate some ammo, buy different ammo, carry on.
if its #2, youre stoned, because pmags tend to just work.
if its #3, or continues to FTE, you have a warranty issue, and youll have a good idea if its the bolt or the upper.
if it'll cycle well after one of those, you'll know who to shake your fist at. I wouldnt go swapping parts until you try more than one type of ammunition. Just a thought.