As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ACFT AIR RETURN DUE TO PRESSURIZATION ISSUES, PLEASE DEBRIEF CREW FOR DETAILS. SEE LOG PAGES 3397569,3397548,3397874, FOR CORRECTIVE ACTION. FOUND TORN FLEX DUCT ON RH ACM CHECK VALVE. RPLD DUCT REF AMM 21-51-15-434-018. NO LEAKS NOTED. PRESSURIZED ACFT, REF AMM 05-51-24-702-001 AND FUSELAGE HELD 4 PSI. NO LEAKS FOUND IN AIR CONDITIONIG COMPONENTS OR FUSELAGE.