If you havn't already, I'd start looking at: 1) Orthogonality, since this is a one-time fix 2) Flexure - this plagues many owners of high-end mounts 3) Alignment - be sure that the "mount" is aligned, no matter what the scope is telling you.
I suggest turning off TPoint pointing correction until you get these 3 resolved.
Dave: the whole point of using TPoint is that it fixes repeatable error. It will guide you in getting polar aligned, and will compensate for non-orthogonality, etc. There is no reason to "turn it off".
