Might be that the arc centers are incorrect in relation to the start and end points of the movement. It only takes an error of .0001" to cause this problem on some unforgiving controllers.
If you want to zip up your nc text file and post it here, someone could run it through a backplot to see how it looks.
Do you have your arc centers set as incremental or absolute coordinates and what does the controller require?
First you get good, then you get fast. Then grouchiness sets in.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)