As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX - FLIGHT 2521- AFTER TAKEOFF RECEIVED A AFT CARGO DOOR CAUTION MESSAGE, RETURNED TO THE FIELD AND ACCOMPLISHED A UNEVENTFUL LANDING. MAINTENANCE FOUND THE HANDLE POPPED OUT. CHECKED DOOR AND SECURED HANDLE WITH NO DEFECTS NOTED. AIRCRAFT RETURNED TO SERVICE. NO PARTS REPLACED.