A little from Beside the Cursor:
Old Revit Problem Resurfaces - 3D Views with Shaded and Wireframe graphics.
Ever had a Revit view that displayed some entities in wireframe while correctly displaying other entities in full shade or realistic mode? I thought this "feature" had been resolved, since I hadn't run into it in ages, but was asked to fix this issue today by a designer. This problem is best shown in the image below, but could be described as wireframe graphics in a shaded mode.
Our issue was not just in a 3D view, but in our Building Sections!
The blog post goes on to mention turning off the cad import. <-----ah ha!
I bring this up because (as I mentioned to Beside the Cursor in the comments section), it happened at our office and I wanted others that come across this issue to know what we did.....
I was approached with the question of why?
After not having a quick fix response (the normal "visibility graphics/ overridden elements/ phases/ worksets changes that users seem to forget), I opened the model at my throne. AHH, the .dwg file I found in plan (zoom extents!) showed a tiny spec as the project. This meant that the Standards for cleaning the imported model were not followed as the entire .dwg file was way too large distance-wise.
(added:)Here is a view of the floor plan:The blue arrow is pointing to our School! (Note the yellow surround for the selected .dwg...and the School is a spec)

A view of some the extra dwg's not placed correctly (there is one in the building that made it in, but sadly, it too is way too large to manage!
:
After having the user hunt down and delete all of the culprit .dwg's, we took it a step further to purge the model. I then opened the model thru Revit, audited it and "saved as" a new Central File.
Come back to Building Sections and...
All was well in model land!
LESSON: KEEP THOSE DWG'S UNDER CONTROL! Follow the steps to ensure they are cleaned up properly and imported correctly.....
thanks Beside the Cursor for bringing this to our attention!