As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) RAMP CHECK CREW O2 WAS 1200 PSIG AFTER 3.5 HOURS WE HEARD A RUSHING AIR NOISE WAS F/O O2 MASK THIS NOISE WAS STOP BY PUSHING TEST BUTTON O2 WAS DOWN TO 72 PSIG (MUST HAVE BEEN SLOWLY LEAKING ALONG THEN FAILED. CREW O2 BOTTLE AND REG. REPLACED. F/O MASK TESTED AND RESET OK.