Thanks jeff for your efforts.
I know there is lots of layers, and also I tried moving everything to a Layer0 which is sketchup default layer I believe but nothing changed in that model that you tried.
Well I realize something I'm not sure about it but, SU automatically smooths some edges I think?
I mean each Height Level (contours) was COMPONENT when I imported from autocad anyway, yesterday I exploded them to make it GROUP to get rid of components, and to make it just single geometry. Maybe that causes such behaviour like this..
Now I think, SU changes or soften some edges in every "make component/explode" situation in bigger geometries, models.
http://thisiso.com/su/ss4.png
This is the model that Im talking about.
I didnt tried on this before, shame for me 😕
If you still interesting you may check this model with unexploded height contours components.
Looks like problem solved spontaneously for me 😮 . fyi, this 2nd model that I upload have much more edges than other. Thanks for your time.