As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW O2 PRESS GAGE READING 0. SAMC TEXT: FOUND 1ST OFFFICER'S MASK LEAKING, SWAPPING THE OBS MASK POSITION TO FO'S POSITION. OBS POSITION IS INOP. SUSPECT DAMAGE DUE TO PRE FLIGHT CHECKS. REPLACED OBSERVERS O2 MASK REF MM-35-12-86 LEAK AND OPS CHECK GOOD. AC OK FOR SERVICE.