Well, there are several things that could be going on. Of course, there is tracking error, which is generally more noticeable on the inner tracks. There is anti-skate force that is an approximate setting, and usually needs more force at the inner tracks than at the outer, and very few arms account for this. Or you could just need to tweak your alignment.
If you wan't to do that, you can read up about alignments on the web. If you make your null points at a different spot with a different alignment, maybe you will like it better. However, the general result is that you just move the problem from one area of the record to another.
Also, you might just be very sensitive to this problem, and might need to eventually go to a linear tracking arm with no tracking error, or a long 12" pivot arm with less tracking error. The longer the arm on a pivot arm, the less tracking error it has.