As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DOOR WARNING LIGHT ILLUMINATED AT 1500 MSL AFTER TAKEOFF. AFT SERVICE DOOR INDICATED IT WAS NOT SECURE, PRESSURIZATION WAS NORMAL. RETURNED TO FIELD. LANDING UNEVENTFUL. PERFORMED STATIC AND DYNAMIC GVI OF AFT SERVICE DOOR. NO DEFECTS NOTED. COMPLIED WITH OPS TEST IAW AMM 52-41-00-710-801. OP'S TESTED GOOD. RETURNED TO SERVICE.