yes they have the same material and the same material id in max.
but every material in max has the same material id unless i explicitly change it.
But why should that make the problem now, when the same model in ue.4.7 was working without flaws.
thx again for helping me with this !
by the way i run into another problem for me.
yesterday arrived my new 4k monitor and its really a lot of fun to work with it 
only thing is working in fullscreen on it with the editor makes things a little to slow for me. 14 fps…
so i went to engine settings and reduced the screen percentage to 50, but that didnt affect the editor viewport at all … the percentage slider isnt working at all for me. no affect hence which number i try…
any ideas ?