Help! Safety Selector Problem

[badmoon692008]

That's your problem. Was this an 80% lower? You can fix it by relieving the selector detent track on the shaft of the selector so that it will point straight up. The mechanical problem you are having is that the flat surface of the selector shaft isn't oriented perfectly flat when on fire, so the trigger trough tail is not able to raise enough to allow the trigger nose to clear the hammer notch.

Nope, this was a stripped lower and matched upper from PF