As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING A ROUTINE FLIGHT, THE ACFT LOST PRESSURIZATION AFTER DESCENDING AND RETURNING BACK TO THE AIRPORT, THE ABOVE LISTED DUCT COUPLING WAS FOUND TO HAVE BLOWN OFF. THERE WAS NO DAMAGE TO EITHER DUCT COUPLING OR CLAMP AND THE PART WAS RE-INSTALLED TO THE CORRECT TENSION. IT APPEARS THAT SPECIAL CONSIDERATION AND INSP OF THE DUCT CLAMP TENSION NEEDS TO BE PERIODICALLY VERIFIED.