As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON CLIMB OUT OF PHX EN ROUTE FOR BOS CREW OXYGEN WENT FROM 1110 PSI TO 420 PSI. TURNED BACK TO PHX FOR REPAIR. MAINTENANCE TROUBLESHOT CREW OXYGEN SYSTEM PER LEAK TEST T/C F8M35301 AND FOUND THE SWEDGES LEAKING ON THE LINES INSIDE BOTH THE CAPTAINS AND LT OBSERVERS OXYGEN MASK BOXES. REMOVED AND REPLACED BOTH MASKS AND BOTH MASK BOXES IAW R1B35301. REACCOMPLISHED LEAK TEST, NO LEAKS WERE NOTED, OXYGEN LEVEL HOLDING STEADY AT 1680 PSI.