As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIR TURNBACK, LOUD BANG AND PRESSURE LEAK AT CARGO DOOR AT FL 270. UNABLE TO MAINTAIN PRESSURE WITH FOUR TURBO COMPRESSORS ON AND OUTFLOW VALVE FULL CLOSE. RETURNED TO MIAMI WITHOUT FURTHER INCIDENT. MAINTENANCE FOUND MAIN CARGO DOOR SEAL TORN AND DETERIORATED IN SEVERAL PLACES. REMOVED AND REPLACED CARGO DOOR SEAL. LEAK CHECK GOOD. PRESSURIZATION NORMAL ON GROUND CHECK. (M)