As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB THE ACFT CABIN WAS UNABLE TO MAINTAIN CABIN PRESSURE. THE ACFT RETURNED TO DEPARTURE WHERE IT LANDED WITHOUT INCIDENT. POST FLIGHT INSP WAS PERFORMED. THE RT FLOW CONTROL VALVE WAS FOUND NOT FULLY CLOSING. RT FLOW CONTROL VALVE WAS REMOVED AND REPLACED. PERFORMED OPS AND LEAK CHECKS, PERFORMED VESSEL PRESSURE DECAY CHECK, ALL CHECKS GOOD. NO OTHER DEFECTS WERE NOTED. ACFT WAS RETURNED TO SERVICE.