As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW O2 LEAK SUSPECTED, O2 SERVICED TO 1700 PSI LAST NIGHT FIRST FLIGHT. THIS MORNING O2 IS AT 620 PSI AND DROPPING FOUND O2 LEAKING AT FO'S MASK BOX SWAPPED WITH OBS POS IAW AMM 35-11-15. OPS CHECK AND LEAK CHECK GOOD. R&R OBS O2 MASK STOWAGE BOX IAW AMM 35-11-15 OPS CK GOOD.