I had a simialr problem with my JR XF631. I had the plane set up for flaperons, and one of my servos had way more throw than the other. I tried several things to get it to work, and I was finally able to fix it by seting the both of the dual rates equal to eachother. Whether this fixes the problem or not, I wouldn't fly until you figure it out. Good luck!

LT-40