As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT/AUTOPILOT STARTED OSCILLATING IN FLIGHT (FL430). THE TRIM CLACKER WOULD ACTIVATE REPEATEDLY TO COMPENSATE. TRIED TAKING A/P OFF AND FLYING MANUALLY AND TRIMMING, THEN REACTIVATED A/P. AFTER A MINUTE THE SAME AS ABOVE OCCURRED. PULLED C/B AND THEN RE-ENGAGED A/P TO HAVE SAME CONDITION OCCUR. FLEW A/C MANUALLY AND FLIGHT CONTROLS SEEMED HEAVY AND HARD TO TRIM. ON LANDING A/C WAS DIFFICULT TO LAND AND CONTROLS EXTREMELY HEAVY.