As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ATTEMPTED AUTOLAND TO 16R SEA AIRCRAFT WAS 6O' LEFT OF CENTERLINE AND DRIFTING FARTHER OFF WITH A MINIMAL CROSSWIND. AUTOPILOT HAD TO BE DISCONNECTED TO CORRECT ONTO CENTERLINE. GROUNDED - YES. REF B737-900 FIM 22-11 TASK 825 PERFORMED LAND VERIFY TEST. ALL TEST PASSED.