Odd Pipe Extensions

Rhino Rhino for Mac
1

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)

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Screen Shot 2018-01-19 at 10.11.56 PM.png1177×759 40.7 KB
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Screen Shot 2018-01-19 at 10.12.15 PM.jpg1242×800 164 KB

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.

47 PM
Screen Shot 2018-01-19 at 10.19.47 PM.png1043×508 81 KB

3

Thanks.

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.