One servo (Hitech HS-81) does not perform like I would expect. It reacts to my commands but occasionally it seems to recenter its self.

I move the radio control stick to full travel back and forward several times and occasionally the servo stops traveling about 20 degrees. This results with my swashplate not being level. This is a newly assembled helicopter and I have never flown.

Is the servo bad or is this a typical result of a newbie not doing something correct?