Hololens - How to render different layers with multiple cameras?

In my scene I have some objects that display machine states at fixed positions. With a second camera I would like to track spheres (with the same positions as the machine state prefabs) that sit on another layer "radar" and display them in my compass.

The result so far is, that it works fine in the unity editor but not on the hololens .. so the question is why?

And my second question is: in general .. is it possible to work with more than one camera when building for hololens?

Here you can see what I get. On the left side is the Unity editor with the prefab that shows the machine state and the "minimap/compass/radar". On the right side you can see this version on the hololens. The spheres on the radar layer are just funky.



My GameObject Management:



My RadarCamera (second camera) settings: