Had multiple end cap strikes on an AAC 7.62 SDN6 before I figured out what was happening. Midway brand AR Stoner 300 Blackout barrel. Sent the suppressor and upper to AAC and they determined that the threads were not concentric. But they fixed it with a new end cap. I cut that barrel in half with a cut off wheel and threw it in the dumpster. Lesson learned on cheap AR barrels.
