As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW O2 AT 400PSI FOUND SOURCE OF LEAK TO BE OBSERVERS MASK WAS NOT IN STOWED POSITION, WHICH CAUSED THE EMERGANCY SWITCH ON THE MASK TO DEPLETE CREW O2. REPACKED OBSERVERS MASK LEAKED CHECKED IN REF TO AMM 35-12-85-910-801 CREW O2 WAS AT 400PSI SERVICED CREW O2 IN REF TO AMM 12-15-21. ACFT OK FOR SERVICE