Odd Pipe Extensions

In the attached file i have two closed curves. I try doing PIPE using 0.5" radius. For some reason the red curve creates the odd extensions at the corner.

What is that?

Oddly, when I copied this shape to a new file to upload here, creates pipe corners for a while then it suddenly started doing this.

Problem Pipe.3dm (3.0 MB)

Here is one where I have copied the curve to a fresh file. After I start playing with it a while it starts doing the extensions.


I am curious why the same shape would work when I copy it to a new file then stop working as I edit the file.