Thumbnail preview issue after upgrading from 2020.1.10f1 to 2020.2.1f1

Hi everyone, I’m wondering if anybody has encountered this issue before and may know a way of fixing it.

Up until I updated my current Unity version, all of my prefab objects thumbnails have displayed with ‘full brightness’ (or lighting turned off).

Here’s what the prefab thumbnails looked like before updating:

And here’s what they look like after updating:

I’ve already tried using Reimport All and Refresh. I’ve also tried messing about with a custom Prefab editor environment and such, but to no avail.

I’m at a loss at this stage as to what is causing this. I have a large number of prefabs that look kind of similar, so rely on the ‘bright’ thumbnails to help me discern details.

I should point out that this preview problem also exists with Materials. Changing a material’s slider makes the material preview appear correct briefly, but once I save the project it resets back to its old thumbnail.

Is this a thumbnail cache problem? Maybe a bug in the latest editor?

I know this seems like a cosmetic issue, but my reliance on needing better visibility of the prefabs means I might have to downgrade back to the version I was using before.

Thanks for any help that can be offered here.

Does anybody have any possible explanations for this? I’ve since been trying various resets of preferences and such but the preview thumbnails remain very dark. Thank you anyone who may have some info.