As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) THE CREW OBSERVED A DOOR WARNING INDICATION AFTER T/O. THE AIRCRAFT RETURNED TO POINT OF DEPARTURE WITHOUT FURTHER INCIDENT. MAINTENACE DETERMINED THE CREW/FREIGHT DOOR WARNING SWITCH TO BE AT FAULT. THE MICROSWITCH AND PLUNGER WERE REPLACED, AIRCRAFT TEST FLOWN AND RETURNED TO SERVICE.