As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) UNABLE TO CONTROL CABIN PRESSURIZATION, CABIN CLIMBING. UNABLE TO CONTROL IN MANUAL MODE. ALL OXYGEN MASKS DEPLOYED AIRCRAFT RETURNED TO DEPARTURE AIRPORT. AIRCRAFT PRESSURIZED ON GROUND WITH APU AND ENGINE BLEED AIR, ALL SEALS ON DOORS AND CABLES CHECKED AS WELL AS SAFETY VALVE, ALL CHECKED SERVICEABLE. NO LEAKS FOUND. PNEUMATIC AUGMENTATION VALVE DOWNSTREAM OF ENGINE CHECKED OK. SYSTEM CONSIDERED SERVICEABLE.