That sounds like your ailerons are not centering properly. That can be caused by hinges that are too stiff, ATV/EPA that is dialed down too far and/or control horns that are too short. Disconnect the pushrods and exercise the hinges for a few minutes and see if they loosen up. Make sure that your linkage setup uses the outer hole in the control horn and allows the ATV/EPA to be set at 100% and you should see a great improvement.

Jim