As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX FLIGHT NR 2415: RUDDER TRIM INOP. AIRCRAFT RETURNED TO FIELD. MAINTENANCE REMOVED AND REPLACED AILERON/RUDDER TRIM PANEL IAW Q400 AMM TASK 27-13-16-000-801 AND 27-13-16-400-801. OPS CHECK GOOD. NO DEFECTS NOTED. AIRCRAFT RETURNED TO SERVICE.