This one looks like a different problem than the other ones, it is not fixed by the tune up that is coming for the next beta. I will probably have to send this example over to the people who make my geometry library to get this fixed, so that will probably be a while.

In the meantime, a workaround for this type of shape is to trim the curves with each other to produce the final outline, then extrude that into a solid with one extrude.

- Michael