Wow!  Thanks very much for such a thorough investigation.  You're right; that certainly seems to be the issue. 

I did submit a bug report.  Please feel free to add this info to that report. 

So, it seems that I need to work in a small scale scene, then come up with some way of importing that into a medium scale scene to incorporate my DAZ figures.

There's a workaround (without having to go back to C5), so that's good!

Thanks again!

 - Dex