My issue is with the rudder servo. After intialisation the tail does not centre but moves hard towards the torque tube. It is in HH mode, but this is uncharacteristic (ie it would normally centre). In flight it needs constant rudder input. Mechanically, the tail set up moves freely, there is no binding/resistance. I appreciate this could be a gyro issue (GP780) but would prefer to see if a new tail servo made a difference. The heli is 8 years old with its original servos.