Problem with preview thumbnails of materials, objects (picture inside)

How to fix it? In 4.16.2 I always see dark preview, same as preview models, very dark view, I don’t change anything to do that, how to fix it?
Plastic_Glossy example:

Anyone? Why if I open it in the editor, my thumbnail goes to dark right after that, maybe there is gamma, or some AA or project settings?

Okay, no help from this forum for so long, I have found the solution, as I understood it’s coming from Forward Rendering option in my project. Thank you very much all!

It’s getting fixed in 4.17.