Yes this one has urk'd me in the past also!

But as already mentioned, a 2-rail sweep will get you what you originally expected.

I didn't know about the micro bevel getting this to work as well?!

-Will

The 2 rail option seems to be the best. The micro fillet forces the sweep to turn a corner, but it's not a clean result - it goes through itself.

Also not mitered as I think that was the intended result.