As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CLIMB OUT, CREW NOTICED OXYGEN REGULATOR AT JUMP SEAT HAD FLOW LEVER IN EMERGENCY POSITION, OXYGEN SYS DEPLETED DOWN TO 75 PSI. THEY RETURNED TO DEPARTURE WITHOUT FURTHER INCIDENT. MX SERVICED OXYGEN SYS, OPS CHECK GOOD IAW MM 35-10-0. ACFT WAS RETURNED TO SERVICE.