As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LEFT PACK OVER PRESSURIZED AND AUTO SHUTDOWN. FOLLOWED MEL PROCEDURES, COULD NOT RESET. RETURNED TO DFW. SWAPPED LEFT AND RIGHT PRSOV'S FROM SIDE TO SIDE. CHECKED SYSTEM FOR LEAKS. CHECKED SYSTEM PER MM 21-51-00, OPS CHECK GOOD. PERFORMED INFLIGHT FUNCTION CHECK OF LEFT PACK FOR HIGH PRESSURE. FUNCTIONS NORMAL FOR SINGLE PACK OPERATION.