It used to be a common defect in the Duchess. The pilot would check full and free movement and in correct sense of rudder, ailerons and elevator as part of the pretakeoff check. As full aileron was being applied the aileron (?) trim would move in sympathy and stay in its last position when the control wheel was centralised. As one LAME told me when I wrote it up in the MR "Don't worry about it, it happems all the time and not worth writing it up in the MR".
. There are cowboy LAME's in the game as well as cowboy pilots.