What was found
ACFT DOOR SEAL OST PRESSURE AT ALTITUDE, THE PILOTS NOTICED A DOOR SEAL WARNING ANNUNCIATOR AND STARTED A DESCENT FROM 41,000 FT. THE CABIN EVENTUALLY STARTED TO EQUALIZE PRESSURE AND THE OXYGEN MASKS DEPLOYED. NO PERSONS HARMED. FURTHER INVESTIGATION FOUND THE BLEED AIR REGULATOR FOR THAT SYS WAS STICKING AND NOT ALLOWING ENOUGH PRESSURE TO INFLATE THE DOOR SEAL FULLY. THE REGULATOR WAS REPLACED AND TEST FLIGHT WAS PERFORMED AT ALTITUDE.