As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING OPS CHECK OF AILERON TRIM SYS, FOUND TRIM TAB ACTUATOR WOULD NOT STOP RUNNING WHEN TRIM REACHED FULL ROLL LT POSITION. REPLACED TRIM ACTUATOR - OPS CK GOOD. REMOVED ACTUATOR, INSPECTION REVEALED ENDCAP AT EXTENSION ROD END TO BE DISLODGED FROM CASE. ROD HOUSING WAS PROTRUDING FROM MOTOR ASSY, WHICH PUSHED END CAP OFF OF HOUSING.