As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING A HEAVY MAINTENANCE CHECK, WHEN THE PASSENGER OXYGEN BOTTLES WERE ACTIVATED THE EMERGENCY OXYGEN MASKS DEPLOYED. THE MANUAL OXYGEN CONTROL CABLE WAS FOUND STUCK IN THE ON POSITION. REMOVED AND REPLACED PNEUMATIC FLOW CONTROL UNIT IAW 352111. OPS AND LEAK CHECK GOOD.