As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT HAD A CABIN DEPRESSURIZATION EVENT CAUSING ALL O2 MASKS TO DEPLOY. THE ACFT WAS FERRIED TO HAVE ALL OXYGEN GENERATORS REPLACED. DURING THIS UNSCHEDULED VISIT AND WHILE PERFORMING MAINTENANCE IT WAS DISCOVERED THAT THE SAFETY CLIP FAILED TO RELEASE AT SEAT 22DEF WHEN MASK DROPPED, CAUSING FAILURE OF THE OXYGEN GENERATOR TO ACTIVATE.