As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 5420. DURING CLIMBOUT OF CVG RECEIVED A CABIN DOOR OUTER HANDLE CAUTION MESSAGE, CREW DECLARED AN EMERGENCY AND RETURNED TO THE FIELD. PERFORMED AN OPERATIONAL CHECK OF THE CABIN DOOR OUTER HANDLE WARNING SYSTEM, DISCREPANCY COULD NOT BE DUPLICATED BY MAINTENANCE, RELEASED AIRCRAFT BACK TO SERVICE.