As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE THE AIRCRAFT WAS UNABLE TO HOLD CABIN PRESSURE AT ALTITUDES ABOVE 10,000. REMOVED AND REPLACED THE R/L FLOW CONTROL VALVES. REMOVED AND REPLACED PRESSURE CONTROL PANEL, CHECKED ALL PRESSURE RELIEF VALVES FOR PROPER OPERATION. THE AIRCRAFT PRESSURIZED ON THE GROUND TO 8 PSI DIFFERENTIAL.