As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING IN FLIGHT USE OF FIRST OFFICERS O2 MASK, NOTICED THERE WAS RESTRICTION TO AIRFLOW DRAW & A PULSED DELIVERY. CONSTANT EMER FLOW WOULD NOT WORK. SWAPPED WITH JUMP SEAT POSITION MASK & OPERATIONS CHECKED NORMAL. REMOVED INOPERATIVE MASK & INSTALLED A SERVICEABLE FULL FACE MASK IN THE FIRST OFFICERS POSITION IAW AMM 35-11-51-2. OPERATIONAL CHECKED GOOD FOR FUNCTION & SECURITY. RETURNED THE MASK REMOVED BY THE FLIGHT CREW FROM THE LT JUMP SEAT POSITION TO ITS ORIGINAL POSITION. OPERATIONS OKAY FOR FUNCTION & SECURITY. OKAY TO CONTINUE.