As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW REPORTED THAT DURING FLIGHT THEY RECEIVED A BLEED ONE LEAK MESSAGE. APPROXIMATELY ONE MINUTE LATER THE CABIN PRESSURIZATION WOULD NOT KEEP UP WITH THE CABIN ALTITUDE. THE CREW RETURNED TO FIELD AND LANDED WITHOUT INCIDENT. MAINTENANCE REPLACED THE Y-DUCT AT THE NR 1 PACK DUAL TEMPERATURE CONTROL VALVE, THE GROUND CONNECTION FLAPPER VALVE AND THE COUPLING ON THE PACK ONE DUAL TEMP CONTROL VALVE.