I have taken a look at this. The issue is the size of the arc that should be where the straight line is. Small arcs can cause a lot of issues to some of the machines we support and it is possible in the offsetting process that we generate lots of these small arcs. Therefore the small arcs are removed and replaced with straight lines. To provide some concrete details, the small arcs deviates from the straight line by less than 0.05 mm or 0.0018 inches which makes it small enough that we consider it removable. We will have a think about this one.
Thanks for the report,