As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
LOST CABIN PRESSURE AT FLT LEVEL 270. CABIN PRESSURE PARTIALLY MAINTAINED DOWN TO 12,000 FT. FLIGHT REQUESTED LOWER ALTITUDE AND RETURNED TO GROUND. AT FL270 THE AIRCRAFT LOST CABIN PRESSURE. CABIN PRESSURE MADE IT TO 12,000 FEET. THE FLIGHT REQUESTED LOWER ALT AND RETURNED TO GROUND. ACCOMPLISHED MT21-001, TESTED OK. CABIN PRESSURE SYSTEM 1 & 2 FAULT. CFDS IDENTIFIED VALVES AS FAULTED. REPLACED OUTFLOW VALVE 10HL PER MM-21-31-51. ALSO REPLACED CPC'S 1 & 2 PER MM-21-31-34.