As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT HYD QTY DROPPED TO 3 WITH AMBER LIGHT ON. GOOD PRESS OF 3000 QTY, NOW MOVING BETWEEN 3 AND 16 QTS. AMBER LIGHT GOING ON AND OFF WITHOUT REGARD TO QTY SHOWING. FOUND LEAKING HYD RETURN LINE ON LEFT REV CONTROL VALVE. TIGHTENED LINE AND LEAK CK'ED GOOD. CLEANED APU INLET AREA, RAN APU AND PACKS. NO FOUL ODOR NOTED IN CABIN.