As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
OXY LOW PRESS MSG IN FLIGHT. OVER 1HR TIME O2 PRESSURE WENT FROM APPROX 1410 TO 1230 PSI. DEFERRED OBSERVERS MASK/SYSTEM IAW MEL 35-10-1 ENTERED IN MMO2 PLACARD INSTALLED. RE-SWAPPED FO'S BOX AND MASK DUE TO CONTROL 3350163-2 WITH OBSERVERS. FOUND LEAK ON FO'S BOX AND MASK. REMOVED AND REPLACED MASK IAW AMM 35-11-12. REMOVED AND REPLACED MASK STOWAGE BOX IAW AMM 35-11-15. OPS TEST OF CREW OXYGEN SYS GOOD IAW AMM 35-10-00. NO LEAKS NOTED AT THIS TIME.