Some prefab previews are extremely dark

I’m using 2018.4.0f1, and some of the prefab previews are extremely dark compared to the rest. All the new prefabs (made after upgrading from 2017.2 > 2018.4) are bright in the Project window, and the older ones are so dark you can barely see what it is:
5856112--622150--upload_2020-5-15_16-45-48.png
How can I fix this?

This problem also happens in 2019.3 (sometimes it will also show pink materials for working textures).

The solution is to reimport all the prefabs, it takes a while but all the previews are bright again.

Reimport All does not work correctly. If you go into each and every folder & subfolder, then select Reimport. this should work.

For the LWRP/URP & HDRP basically all assets are useless for me, they appear pink or black/white and when I drag one to the scene, they are still pink, black/white.

This is the barebones HRDP/LWRP demo scenes, fresh out of the box for 2019.3.14f.

After Reimport.

I can’t work on anything but the standard pipeline.