As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) CREW REPORTED A BANG AND THEN UNUSUAL PRESSURIZATION RATE. THE AIRCRAFT RETURNED TO THE POINT OF DEPARTURE. MAINTENANCE DETERMINED THAT THE AFT CANTED BULKHEAD BLOWOUT PANEL HAD RELEASED. FURTHER INVESTIGATION REVEALED THAT THE AFT CARGO DOOR SEAL WAS LEAKING. THE BLOWOUT PANEL WAS RE-INSTALLED AND THE AFT CARGO DOOR SEAL WAS REPLACED. THE AIRCRAFT WAS SUBSEQUENTLY RELEASED FOR SERVICE.