As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU CHECK VALVE LOCATED ABOVE APU LOAD CONTROL VALVE FLAPPERS HAVE WORN THRU RETAINING PIN CAUSING FLAPPER TO COME LOOSE AND DROP DOWN INTO THE BUTTERFLY MECHANISM OF THE LOAD CONTROL VALVE. THIS CAUSES THE LOAD CONTROL VALVE NOT TO CLOSE.