As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PILOT REPORTED THAT THE CABIN ALTITUDE STARTED TO CLIMB HIGHER THAN SET UNCOMMANDED. DURING AIRCRAFT DESCENT, THE CABIN AIR INDICATION WOULD FLUCTUATE, CLIMBING AND DESCENDING. INSPECTION DISCLOSED A PRESSURIZATION DUCT IN THE ENGINE COMPARTMENT HAD SEPARATED.