Material sometimes black sometimes wood, same layer

Hey,
I just startet using D5 and have a really really weird bug.
I have some objects, for example windows all in the same layer with the same material colour in rhino (RED), now it works for some windows and I can put a glass material on top, and for some it stays black and if I try to put a material on it, it puts it on all of the rest of the scene too.

If I remodel some of it and put it in the layer it suddenly works again??

Is this just a rookie mistake from my side or what could it be?

Thanks for your help, have a nice day!

Hi,

Parts with the same material in the modelling software will be recognized as a whole after importing into D5, if you want to keep them independent, you need to give them different materials/colours in the modelling software first, and then reapply other materials in D5.