As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CLIMBING THROUGH FL200, PLANE MADE A YAW TO THE RIGHT SEVERAL TIMES. TURNED OFF THE AUTOPILOT & TRIMMED THE AIRCRAFT, THEN TURNED ON THE AUTOPILOT. AIRCRAFT BEGAN YAWING TO THE LEFT. CHECKED AOM-1 FOR GUIDANCE, THEN DECLARED THE EMERGENCY & RETURNED. YAWING DECREASED UNTIL ABOUT 300 AGL & KICKED A COUPLE OF TIMES & YD1 INOPERATIVE, STATUS MESSAGE POSTED. R & R NR 1 YAW DAMPER LINEAR ACTUATOR IAW AMM 22-22-01. OPERATIONS CHECKED GOOD, NO FAULTS FOUND.