As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WHILE IN CRUISE AT FL280, THE CAIBN ALTITUDE CLIMBED AT 8000-9000 FPM TO 11,000 FEET. CREW INITIATED EMERGENCY DESCENT TO 10,000 FEET AND CABIN STARTED DESCENDING. LEFT PACK VALVE WENT TO FULL HOT. FLIGHT CONTINUED TO DESTINATION AND LANDED WITHOUT INCIDENT. MAINTENANCE FOUND A CANNON PLUG LOOSE ON THE LEFT PACK SHUTOFF VALVE AND CORRECTED IT. ALSO, REPLACED THE LEFT PACK PRESSURE REGULATOR AND SHUTOFF VALVE. AIRCRAFT RETURNED TO SERVICE.