As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) CABIN ALT WARNING AT FL 330. IMPOSSIBLE TO CONTROL CABIN PRESSURE IN MANUAL MODE. PROGRESSIVE RETURN TO NORMAL PASSING THROUGH FL 220. PRESSURE REGULATOR AND RELIEF VALVES REPLACED. NEXT FLIGHT EXPERIENCED SAME MALFUNCTION. AIR INLET DUCT FOUND DEFECTIVE AND REPLACED.