Is it possible that you performed polar alignment on the wrong star?
I live in the southern hemisphere and Sigma Octantis is difficult to identify, especially in an area of high light pollution. When I first received my Mach1 it took a little while to make the polar alignment and I was using the wrong star, so my GOTOs were quite wrong and the tracking horrible.
But once I identified Sigma Octantis correctly and performed the polar alignment (and later Sync), it was like magic, the GOTOs were accurate and the tracking perfect.
And if you use SGP and Plate Solving is more "magic", incredibly accurate. SGP and Mach1 seem to be made for each other.
(By the way, I wasn't using RAPAS, I already had a PoleMaster and I used this one).