As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 4089 - AFTER TAKEOFF, 'BETA' HORN SOUNDED, CREW UNABLE TO CANCEL HORN, ELECTED TO RETURN TO FIELD. AIRCRAFT LANDED WITHOUT FURTHER INCIDENT. DAY MAINTENANCE INSPECTED AIRCRAFT, DISCOVERED A DEFECTIVE MICROSWITCH ACTUATOR. MAINTENANCE REPLACED ACTUATOR IAW MM 27-00-00. GROUND CHECKED GOOD. AIRCRAFT RETURNED TO SERVICE.