Add Detail Mesh acting strange on Unity 5.4.2

Hi,

what I doing wrong or is this some kind of bug. In the middle you can see a rock added to scene normally from the project window. Those rocks around it are added via terrain Paint Detail tool. In Edit Detail Mesh I have tried to drag the model from the hierarchy and from the project window. The result is the same both ways. There is some green stuff which comes from grass texture and has nothing to do with rock texture.

Can anyone help me out?