try disocnnecting the two servos and switch the channels they are on. the left one will go on the right ones channel and vice versa. Then see if the problem switches with the servos. if the other side has the problem, then you know its your radio setup, if the same servo is still leading then you know its the servos. get what i am saying? if not then i will try and explain more.....just flip flop your connectors basically...

sean