If that is where you run your antenna, the trouble may be simply to low a signal to noise ratio (dropout) and the wing drop is the receivers response to such.

My observation is on landing (when you seem to have the most trouble) The antenna is pretty mush behind the wing, and very near the rudder and elevator servos.


Run the antenna from a hole in the wing (or tape it to wing) at a point right behind the wing servo and run it up to the top of the vertical stab (fin). you can tape it there or use a bit of fuel line and a pin to mount it. I'll bet this takes care of it