As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ORD - CREW REPORTED DURING THE AUTOLAND WITH DIRECT FLIGHT GUIDANCE SYSTEM ONE SELECTED THE AUTOPILOT PULSED AT 50 FEET AND THEN DISCONNECTED. FLIGHT ACCOMPLISHED A GO AROUND AND LANDED ORD WITHOUT INCIDENT. AIRCRAFT REMOVED FROM SERVICE. REPLACED ELEVATOR SERVO DRUM ASSEMBLY. SYSTEM GROUND CHECKED NORMAL OPERATION.