Since most everybody that deals seriously in airsoft is a regular visitor to this board, particularly the gearbox techs, I'd be careful what I called them lol...
That said, are you backing the screw that adjusts the hop up all the way in, or out? On the M14 it was kinda counter intuitive to me. Other than that, it could be how the mag is seating; if it isn't seating properly, the feed lip could only be depressing the stopper at the top of the mag when you actually put the mag in place, and then sliding back out after you let go.