Your dish size and location could play into it. It is my understanding for ku signals the larger the dish the aiming has to be more precise or you do bring in more than one satellite. Plus, from my own experience here in w. tx. at 102, the further east or west I try to go the less I have to move my 90cm dish due to the angles involved, etc.
Like Pete, a lot of times when I try to aim at g10 at 123, I actually hit 121 due to the stronger signal on meter, so all I have to do is just barely bump my dish to bring in g10.