Have you calibrated the sticks with dipswitch 8? I've found that doesn't always take unless I do it exactly right. I turn on TX, then tank, then throw dipswitch 8, move the sticks, throw 8 back, turn off tank, turn off TX, turn TX back on, turn on tank. For me engine start is left stick up and right, and headlights are down and right. I usually try the lights to see if the stick calibration worked. Are you hearing a one second burst of elevation noise when you first turn on the tank?

EDIT, and try swapping out the servo cables. Those are known to cause trouble sometimes.