I'll pretend to be jorb and say, reported before, will fix ... eventually xD
My guess is they check for fleeing conditions before they check for rage conditions. Either that or they can't figure out pathing the split second they decide to enrage, so they enrage and run instead of enrage and attack, tho that last one seems less likely as they often recalculate and turn around to swipe people's face off.
"The psychological trials of dwellers in the last times will be equal to the physical trials of the martyrs. In order to face these trials we must be living in a different world."