Just to clarify: you are talking about elements created with the Object Tool, right?
Because in case of most 3D element types, such as Walls, Slabs, etc. they are converted to Lines and Fills when pasted into a Worksheet Viewpoint and that changes their Classification and Properties as well.
In the case of Object elements, I see that their Classification becomes "Unclassified". I suppose this is what you are talking about?
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