As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING CRUISE FLIGHT AT FL180 THE CARGO DOOR WARNING LIGHT CAME ON. CREW FOLLOWED EMERGENCY CHECKLIST PROCEDURES AND STARTED DESCENT. THE LIGHT WENT OUT AT 500 FT AGL. CREW LANDED WITH NO FURTHER INCIDENT. THE DOOR WARNING SWITCH ACTUATOR FOR THE LOCK WAS FOUND SLIGHTLY WORN AND HAD CAUSED THE SWITCH TO GO OUT OF ADJUSTMENT.