As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON DESCENT INTO IFP, AIRCRAFT HAD UNCONTROLLED, MILD DUTCH ROLLING (LATER DESCRIBED AS FISH-TAILING) WITH AUTO-PILOT DISENGAGED. EXTENSIVE TROUBLESHOOTING REVEALED AN ANOMALY WITH THE MAIN RUDDER PCU YAW DAMPER SERVO CONTROL AS INDICATED THROUGH THE YAW DAMPER COUPLER BITE FUNCTION (REF: B-737 MM 22-12-01, PAGE 12). THE MAIN RUDDER PCU WAS REPLACED PER B-737 MM 27-21-91. SUBSEQUENT YAW DAMPER COUPLER BITE TESTS REVEALED NO FURTHER DISCREPANCY. THE AIRPLANE WAS TEST FLOWN AND RETURNED TO SERVICE.