As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FLIGHT CREW REPORTED THEY EXPERIENCED A CABIN OVERPRESSUREIZATION OF 9.0 PSI AT CRUISING ALTITUDE OF FL400. THEY INDICATED THEY WERE ABLE TO CONTROL AND ARREST IT WITH MANUAL PRESS - MODE. THE MAINTENANCE TEAM REMOVED AND CLEANED AND REPLACED THE THE CABIN PRESSURE CONTROLLER. OPS CHECKS WERE SATISFACTORY. THE AIRCRAFT WAS RETURNED TO SERVICE.