As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) DURING TROUBLESHOOTING OF AIRCRAFT FOR A PRESSURIZATION DEFECT, IT WAS NOTICED THAT THE RT ACCOUSTIC MUFFLER INTERIOR LINING HAD BECOME DETACHED. THE PIECES WERE FOUND BLOCKING THE PRIMARY HEAT EXCHANGER. THIS WAS DETERMINED TO BE THE CAUSE OF THE PRESSURIZATION DIFFICULTY. THE MUFFLER WAS REPLACED. PARTS WERE REMOVED AND AREA CLEANED. AIRCRAFT RETURNED TO SERVICE.