Thanks for reporting this Thor, I should be able to fix it for the next beta.

It is related to having exact arc curves on opposite sides. Sometimes these curves have to be treated a little differently when multiple curves are being combined together into one.

One of the next things I am going to work on is a better way for synchronizing multiple curves together - this work will help out in this situation and also for sweep and loft as well.

At the moment, if you actually add a 3rd section running down the middle, it will actually work better for this particular situation with arcs on both sides.

- Michael