As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WOULD NOT MAINTAIN CABIN ALTITUDE/PRESSURE IN AUTOMATIC OR MANUAL MADE AT FL290. A/C DESCENDED LOWER TO ENABLE MANUAL PRESURIZATION; THUS NORMAL/OPTIMUM CABIN ALT/PRESSURE FOR CREW AND PASSENGERS. ALL MASKS FELL. CORRECTIVE ACTION: REMOVED AND REPLACED RIGHT PRESSURE VALVE DUCT; FORWARD RELIEF VALVE, AND RIGHT AIR CYCLE MACHINE.