Hi Steve, that is odd, definitely seems to be a bug. It appears to be getting confused about whether the ends are closed or not in those cases.

It looks like the Planar command can cap it successfully though, so to fix it select the uncapped pipe and run Construct > Planar - that should fill in planar surfaces at the uncapped ends.

I've added this to my list to look at in v3, thanks for reporting it.

- Michael