Robot's name was "Gort", I believe.

1/4" is a lot of aileron, so warp sounds the most likely.

Having the wing mounted crooked, so one side is further forward, will also give a slight roll; and a dutch roll in turns.

Have you checked the aeroplane by holding at the spinner and rear fuselage tip to check if it is in balance around the long axis? One side of the wing could be heavy.

Just some additional things to check.