I don't recall seeing this before & can't duplicate it with the same files my user is opening.

We have PDM, I have the latest version, so does the user.
The box in the Title Block is referencing a model custom prop 'Reference Drawing'.
 $PRPSHEET:"ReferenceDrawing"
The custom prop is only present if used, and it is currently not used (doesn't exist) in the model.

User is getting ERROR!:ReferenceDrawing