Diagnosis check...bolt speed?
A friend of mine had these exact malfunctions on a PSA upper while running PMC bronze. We ruled out mags, lowers, BCG's, everything but the ammo.
It would run on full pressured ammo just fine and even cheap Herters/Tula, but not PMC.
He sent it back to PSA and they replaced the gas tube, even though we could find no excessive gas leakage and they polished the feed ramps a bit, but it still doesn't like the PMC. It will bolt override about 2 times per magazine.
Strangely enough, the same lot of PMC will run in all 3 of mine. Two BCM middies AND a PSA middie.
Kind of bizarre.