I'm currently busy on a project and am strugling with some join/visibility issues.

I have a concrete floor with some sloped concrete on it and tiles on top. In a previous project i used the concrete as my structure floor and the ones on top as a layered floor family (sloped concreted with tiles on top). Now as i joined the concrete floor with the sloped concrete the bottom of the sloped concrete dissapeared (as i wished). Now i'm in a new project and am doing exactly the same but the material of the sloped concrete and the tiles changes to the material selected in the object style.

I don't know what i'm doing differently. I checked all the settings of the families and visibility settings and it's all the same. Someone who can help me or has some advice on this? Thanks!

What's happening:

How it should be: