Linear forms left open by clip volume

Hello,

I have a problem using clip volume on linear forms. See the attached PDF : standard Microstation extruded elements get clipped OK (using the cut plane settings), but linear forms are not (they appear as open on the cut plane). When the view is promoted (in BA), the clip is OK, but the material assignment disappears!! So both ways the result is not good. On page 2 of the PDF you can see an example from one of my projects: in SS1 all was OK !!
I wonder if this is a bug or am I doing something wrong?  TIA   André