As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON CLIMBOUT OF 21,000 HAD A VERY LOUD WHINE COMING FROM RT FWD EMERGENCY EXIT CABIN DIFFERENTIAL WAS 4.5 PSI CABIN ALT WAS 6000. RETURNED TO FIELD. LANDING UNEVENTFUL. INSPECTED DOOR SEAL AND MATING SURFACE, RECONTOURED SEALANT AT UPPER AND LOWER DOOR INTERSECTION. CHECK FLIGHT, OK RETURNED TO SERVICE.