As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT CABIN ALTITUDE CAUTION MESSAGE, DESCENDED TO FL 240 DURING DESCENT CABIN ALTITUDE CLIMBED QUICKLY AND MASK DROPPED. RAN QRH FOR EMERGENCY DESCENT. DIVERTED, FOUND A LARGE PIECE OF INSULATION BLANKET STUCK IN THE PRIMARY OUT FLOW VALVE, NOT ALLOWING IT TO MODULATE PROPERLY. REMOVED PIECE OF INSULATION BLANKET AND RESECURED INSULATION. PERFORMED PRESSURIZATION CHECK, PRESSURE CHECK GOOD AT THIS TIME.