As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE NOTICED HYDRAULICS DECREASING. FOLLOWED POM PROCEDURE AND DEPRESSURIZED AND ISOLATED THE SYSTEM. FOUND BOGIE UNLOCK CYLINDER RELIEF VALVE ON LEFT MAIN FEAR STUCK OPEN. REPLACED RELIEF VALVE POF 32-53-02. NO LEAKS DETECTED. HYD WAS SERVICED.