As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON CLIMB OUT KDRT, AIRCRAFT BEGAN ALTERNATING LEFT/RIGHT YAW EVENTS WHICH CONTINUED THROUGHOUT FLIGHT WITH AUTOPILOT ON OR OFF. UNSCHEDULED LANDING KSAT. CORRECTIVE ACTION REMOVED AND REPLACED STAB AUG COMPUTER AND PERFORMED OPS CHECKS IAW DC9 AMM 22-11-1. OPS CHECKS GOOD.