if there is a family instance which contains any material with smooth enabled, when it is rotated more than 90 degree, the normals of the vertical faces will be mistakenly reversed then the smoothed suface will be corrupted in the rendering, though the model's geometry is actually fine.
fig.1 A family instance contains a material with smooth enable
fig2. to compare with the first instance, second one is copied with no rotation, both fine
fig3. the second instance rotated 90 degree corupted faces appears,
fig4. 180 degree, the suface appears ugly edge
Here is the revit file with the family instance
Supermicro 4028GR TR2|Intel xeon E5 2697 V3| windows 10| revit 2019 |Titan V+ Quadro GV100+RTX 2080 Ti