As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SERVICE DOOR CAUTION DURING CLIMB OUT, RAN QRH, DECIDED TO COME BACK TO CHICAGO. FLT 5784. INTERROGATED MDC, FOUND OUTER SERVICE DOOR HANDLE SENSOR OUT OF RIG, VERIFED HANDLE WAS CLOSED DEFERRED SERVICE DOOR INDICATION SYSTEM PER MEL 52-70-5A PLACED REQUIRED PLACARDS.