Does the stick move normally?? Are you saying that it won't return to center otherwise??? If this is the case it sounds like the centering spring for that stick as come off. Carefully remove the back of the radio and see if the spring is missing. If you haven't used this radio yet it must still be new right??? You should be able to have Futaba take care of it under warrenty if it's anything more than the spring coming off.

Ken