As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER CHANGING O2 UNIT ON PREVIOUS WRITE UP, AIRCRAFT SHOWED APPROX 174. DURING FLIGHT NOTICED O2 AT 1040 AND DROPS APPROX 10 PSI EVERY COUPLE MIN. OXY LOW PRESS CAUTION ON FAIL AT GATE 880PSI. FOUND FO'S BOX AND MASK LOOSE REINSTALLED FO'S BOX AND MASK REF MM 35-11-12. SERVICED CREW O2 REF AMM 12-16-35 TO 1625 PSI A/C OK FOR SERVICE.