As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE CREW NOTED AN UNCONTROLABLE PRESSURE RISE ON TAKEOFF. THE CREW RETURNED TO MEM AND LANDED WITHOUT INCIDENT. MAINTENANCE RELEASED THE AIRCRAFT IAW MEL. MAINTENANCE TIGHTENED A LINE ON THE PNEUMATIC OUTFLOW VALVE, PERFORMED A OPERATIONAL CHECK OF THE PRESSURIZATION SYSTEM, NO DEFECTS NOTED AND THE AIRCRAFT WAS APPROVED FOR RETURN TO SERVICE.