As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PRESSURIZATION SYSTEM PROBLEMS. INVESTIGATION FOUND INBOARD AND OUTBOARD POSITIVE PRESSURE RELIEF VALVES TO BE UNSERVICEABLE. BOTH VALVES REPLACED. OUTBOARD VALVE CURRENTLY CONSIDERED TO BE THE PRIMARY CAUSE OF THE CABIN DEPRESSURIZATION EVENT.