Michael,

The clipping issue has persisted in SU for so long and through so many versions that it's almost hard at this point to call it a "bug." Unfortunately, it's more like a fact of life. I see correspondence on the Pro forum about this phenomenon going back to Version 2 in 2002, and there are explicit acknowledgements of the problem from various @Last personnel from the same time period, along with assurances that they'll try to get it resolved by the "next release."

One wonders if it's still reasonable to be looking for a fix any time soon; it would seem that if it hasn't been fixed by now it may well never be.

The generally accepted workarounds seem to be working in perspective mode rather than paraline, using a narrower field of view, and using Zoom Extents to reset the clipping plane.

-Gully