no valid edges for cosmetic thread creation found

Tube frame.
Tapped holes after welding the frame.
It's a simple assembly of square tube stock.
We add the holes using the hole wizard and get this error messageon several holes
"no valid edges for cosmetic thread creation found"
Those holes don't appear. We can create a second set of holes thatcontains only the failed holes in the EXACT same location, and thesecond set works.

What does this error mean?
How can we avoid it?

I will add that a surface is selected before calling up the holewizard - the position sketch is a 2D sketch. All faces in questionare co-planar and all holes and cosmetic threads are intersectingplanar surfaces.SolidworksAssemblies