As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PASSING FL 210 AFT SERVICE DOOR ACTIVATED FUSEAGE MASTER WARNING. DIVERTED AND ACCOMPLISHED UNEVENTFUL LANDING. AIRCRAFT REMOVED FROM SERVICE. FOUND AFT SERVICE DOOR EXTERIOR HANDLE NOT FLUSH. COMPLIED WITH OPS TEST OF SERVICE DOOR, OPS CHECKED GOOD. NO FURTHER DEFECTS NOTED IAW AMM 52-41-00-720-801. RETURNED TO SERVICE. NO PARTS REPLACED.