As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SAN - FLT 1412 - ON CLIMB-OUT, SQUEAL WAS HEARD OUT OF THE L1 DOOR. AT FL 330 IN CRUISE, CABIN PRESSURE BEGAN TO CLIMB. FLIGHT RETURNED TO SAN WHERE LANDING WAS WITHOUT FURTHER INCIDENT. MAINTENANCE REPLACED FORWARD ENTRY DOOR TOP HINGE COVER. (M)