As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PAX DOOR OUTER HANDLE CAUTION MESSAGE APPEARED IN FLIGHT COMPLIED WITH QRH AND LANDED AT NEAREST SUITABLE AIRPORT DURING CLIMB THR FL210. INSPECTED PAX DOOR LOCKING MECHANISM, NO DEFECTS NOTED, CYCLED DOOR CLOSED AND OPEN SEVERAL TIMES. NOT MESSAGE APPEARED ON GROUND.