Ok, it seems to be a bug too...
If I in the cloned Cellos instrument (that has the Violas range) try to load the factory preset 04 Cellos-8 VelXF the Violas range retains. And it doesn't matter what factory preset I load. The range is still the one I cloned from the Violas.
The only workaround I find is to create an new instance and load the factory preset, then the range will be correct. But in that case I have to redo all routing of the individual microphones in VEP.