Can't Import dwg with xref exported revit dwg

[t1.shep]

We're working with a consultant by exporting dwgs from our Revit file. When I attempt to import/link their file, which has our exported dwg as an xref, I get a "can't import file" error. When I unload or delete the xref'd file then it works.
I guess this is fine, as I really only need what they've drawn on top of our file, but why do I get this error? Do I only get this error because the xref file is from the revit file? I don't get the error in other dwg files with xref'd ACAD files.

[MNsnowtaTy]

I believe it is because you have exported the Revit File to CAD, and then now you are just importing what you already had exported out. So you would just want to bring in the new work.