Thanks for all the info, Michael.

You asked: Does this happen when your object was originally a joined solid in MoI as well?

Yes, always separate pieces, even if they were all joined in MoI.

One long way around which seems to produce good results is importing the Stp file into Alibre and then exporting that same file from Alibre in SAT format to open in TurboCAD.

At any rate, there is still a lot of learning and experimenting to do, so maybe I will eventually work it out.