As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING TEN DEGREE RIGHT TURN EXPERIENCED FULL YAW DAMPER DEFLECTION TO THE LEFT. AUTOPILOT WAS ON, RUDDER AND AILERON TRIM WERE SET AT ZERO. SIGNIFICANT AILERON REQUIRED TO KEEP AIRPLANE LEVEL UNTIL YAW DAMPER WAS TURNED OFF. *S/D* REPLACED YAW COUPLER. YAW COUPLER HAD RATE GYRO MALFUNCTION, SYSTEM CHECKS OK.