As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING THE OPERATIONAL/LEAK CHECK OF THE DOOR SEAL SYSTEM IT WAS NOTED THAT THE DOOR SEAL WOULD NOT INFLATE. A HISSING NOISE (ESCAPE AIR) WAS NOTED AND TRACED BACK TO THE DRAIN VALVE (PN: 510343-1), THE STEM CAP WAS BROKEN OFF. ALL PARTS WERE RECOVERED. THIS WAS DISCOVERED DURING THE FIRST CLASS MOD.