As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CREW O2 AFTER TAKEOFF DROPPED AT A RATE OF 10 PSI PER MIN. AT TAKEOFF O2 LEVEL WAS 1850 AFTER 2 HRS OF FLT O2 HAD DROPPED TO 1380 PSI. FOUND BOTTLE REGULATOR FITTING LEAKING. REPLACED FITTING O-RING SEAL, SERVICED BOTTLE TO 1760 PSI AND LEAK CHECKS OK.