As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 3218 - IN CRUISE FLIGHT FROM MSP, THE PRIMARY AND SECONDARY CARGO DOOR WARNING LIGHTS ILLUMINATED. THE AIRCRAFT RETURNED TO MSP WITHOUT FURTHER INCIDENT. MAINTENANCE ADJUSTED THE CARGO DOOR HANDLE WARNING SWITCH. SYSTEM OPERATED SATISFACTORILY. (W)