As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT RETURNED TO DEPARTURE DUE TO OSCILLATION WITH BOTH YAW DAMPERS ENGAGED. WITH THE RIGHT YAW DAMPER DE-SELECTED, THE OSCILLATION STOPPED. EMERGENCY DECLARED. LANDING UNEVENTFUL, AND AIRCRAFT WAS GROUNDED. REMOVED AND REPLACED AIR GROUND RELAY K199 (AALA20171105005) AND RELAY K293 PER FIM 22-21-00. NO FAULTS NOTED. OPERATIONAL CHECK GOOD.