Preview window for selected prefabs is broken

Unity Engine
1

If I will select several prefabs, here what I will have in preview window:

3496434--278571--2018-05-14 16_43_15-NVIDIA GeForce Overlay.png

There is two problems:

  1. Each prefab displayed in each mini window on each other
  2. Background of preview window is incorrect. It is too light, be default it should be darker

This problem exist only in single Unity project, if I will create new project - everything is okay.
However this is a big project so I can’t just recreate it manually.
Even if I will delete project folder and will download it from the Collaborate - the problem still persists.

Besides that, sometimes Unity Editor crashes for no reason, it happens only in the same project. Maybe it is caused by the same error.

Unity version 2017.1.0p4

Any idea how I may fix it?

2

Are you using Layer 31 for anything?

3

Thanks for reply.
No, only layers 0-12 used.

But I found that this problem is fixed when project updated to latest Unity 2018 version. Of course I am curious why it is happened in version 2017. but still, it could be a solution.