As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
1)ON CLIMBOUT CREW NOTED CABIN PRESSURIZATION NOT HOLDING CORRECT CABIN ALTITUDE. 2)CREW RETURNED TO HOME BASE. 3)MAINTENANCE TROUBLESHOT AND FOUND THE AIR CYCLE MACHINE DUCT COUPLER COMING LOOSE. 4) RESECURED DUCT COUPLER, OPS CHECK GOOD.