As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW O2 READS LOW. SUPPLEMENTAL DATA UPDATE, ISOLATED O2 LEAK TO FIRST OBSERVER'S O2 MASK. WITH MASK PLUGGED INTO FITTING MASK LEAKS. WITH MASK UNPLUGGED FROM FITTING NO LEAKS FROM FITTING. NEEDS NEW FITTING ASSY. REPLACED 1ST OBSERVER'S OXYGEN FITTING. LEAK CHECKED SYS CKS GOOD.