As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FLIGHT CREW REPORTED THAT DURING PREFLIGHT CHECKS FINDING THE LEFT SIDE, CAPTAINS OXYGEN MASK HARNESS DOESN'T EXPAND AND OPEN CORRECTLY. TUBE IS BULGING OUT OF TORN FABRIC ON HARNESS. THE BASE MAINTENANCE TEAM REMOVED THE PILOTS MASK AND INSTALLED AN OVERHAULED MASK. OPS CHECKS GOOD. AIRCRAFT WAS RETURNED TO SERVICE.