As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 5042 - AFTER TAKEOFF ENGAGED AUTO PILOT AT 12000 FT, AT 20000 FT FELT SLIGHT VIBRATION AND YAW MOTION. EICAS SHOWED AILERON FLUTTERING. REPLACED AILERON SERVO, INSPECTED AILERON AND RUDDER CONTROL SYSTEMS AND PERFORMED AUTO PILOT OPERATIONAL CHECKS. NO FURTHER DEFECTS.