You may need to see how you're mixing the second aileron channel to the first one. For two aileron servos operating off of one channel, you'd turn on either the Flaperon function or the Aileron Differential function. Make sure the endoints for both channels are set to the same amount, and that the mixing function is properly-set. Also, please make sure that the sub-trim for both channels is set as closely to zero as possible.

If all else fails, you can reset the model memory to defaults and start over. To get the results you're seeing, one of your functions is not set correctly.