As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BTM - RETURN TO FIELD, MAIN CABIN DOOR LIGHT CAME ON AFTER TAKEOFF. LANDED WITHOUT INCIDENT. INSPECTED DOOR OPERATION. TESTED GOOD PER MEL PROCEDURE 52-2. FORCE INTERNAL LOAD 43 LBS EXTERNAL 35 LBS, NO DEFECTS NOTED. NO PARTS REPLACED.