I wouldn't worry so much that you only have the problem on the ailerons as much as the fact that you have the problem at all. Mechanical problems and connections aside ( I'll assume they have been checked) I suspect the Ridge ignition and especially that coupled with the Rcexl opto-kill as the source of the problem. As others have said, try removing the kill switch and see if there is a change. From there, I'd replace the Ridge ignition in a heartbeat ... the engine will run better anyway as you'll gain an advance curve in the process. You'll have more power and a smoother idle!

Of course I assume the obvious things have been checked such as a resistor plug is being used? Any shielding and grounds are connected properly, etc.