I did figure out how to resolve this and it was time consuming and not easy. In short there was an AutoCAD DWG definition buried in one of the families. The family was not being used but it was in the project. The process for finding the culprit was one of purging and narrowing down to the offending family. I first purged everything and checked to see if the DWG was gone from Object Styles, which it was. I then did an undo and began purging/undo each family category one by one to see which category held the DWG. I continued that process until the family was found. It's bonkers to have to do this (I just wanted to say bonkers). The problem is the database does not see or report these DWGs that are buried in unused families. If it did it would be sooooo much easier to find and purge. Also, the DWG definition does not show up in Object Styles under Imported Object Styles which could send one on a wild goose chase. Hope this helps you other OCD Revit people out there...
