If I remember correctly (I'm at work now without my Tx) the inhibit Aux 2 function is accessed by turning on the Tx with both the buttoms pressed. In this mode make sure that you have the correct model selected then scroll through the options until you get to the correct on.

Your problem with 1/2 movement may be because you have the Aux2 switch in the wrong position, inhibiting should fix it though.

Terry