As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) APPROXIMATELY 1HR INTO FLIGHT CREW REPORTED CABIN PRESSURE VALVE NOT CLOSING. CABIN PRESSURE ABOVE NORMAL. CREW PATCHED TO MOC VIA DISPATCH AND DECISION MADE TO DIVERT BACK TO THE AIRPORT. RESOLUTION SAFETY VALVES 6HL AND 7 HL REPLACED IAW AMM 21-31-52 FUNCTIONAL TEST OF THE POSITIVE AND NEGATIVE DELTA P PROTECTION OF THE SAFETY VALVES C/OUT IAW AMM 21-31-00-720-001A.