Materials turn black in inspector and project, yet normal in editor, possible bug

everything was just fine, then sudennly, this bug showed up. I didn’t do anything weird at all. This is a standart URP project in Unity 2020.3.17f1. Updating it would make a mess for my workflow. This never happened before in years.

Now, any material you click on in the project window turns black both in inspector and preview. Strangely, it looks just fine in the editor window like it used to, but in the inspector it’s ALMOST black. Only illuminating materials are not affected. Refreshing and reimporting doesn’t help. But! If you save your current scene, all material icons turn normal again, untill you click on them again. It’s like lights out or something, what happened…?

I couldn’t find any situations like this one described.
No error messages occur in the console.

Example: Kurb is the red-white material, yet it’s displayed like this now. It’s fixed if you save the scene, but it will become black again as soon as you click on the material icon. Mat - road material. If I would click on Misc - the preview and inspector material would turn black. Materials in the editor are unsaffected by this, and they are just as good as they were. It’s like somehow I lost my light in inspector.


Video for better understanding of my issue

My colleague had this issue. Seems like you can just edit the material in some way and save and it will start working again. But you have to do this for all materials that are “bugged”. Another way is to just edit all materials .meta files by just adding a space in them.