Thanks for taking the time to explain all of this, Michael.
Even though I'm not a licensed user of MoI I like to look in on this forum as it's friendly and informative. In fact, it's not unknown for me to direct some of the more interesting topics and innovations here, over to the ViaCAD forum. So I hope none of you mind an interloper in your midst.
The only thing that's still a little puzzeling, is that none of these artefacts seem to show in the Surface Analysis tools that are part of ViaCAD Pro. So does that mean it's just a display 'feature' rather than something fundamentaly wrong with the geometry? I include a couple of Zebra screen shots for reference.

Martin.