PDF thumbnails inside of a white square

[Irriducibile]

Hello

Suddenly, my pdf thumbnails appear inside of a kinda white square, like this:

I have no idea why this started happening, but installing an older Adobe Reader version has not helped and I cannot undo the most recent Windows update anymore.

I've tried these, but neither helped:
- Clear Thumbnail Cache
- Delete IconCache.db
- Use this Fix
- In Adobe Reader, turn off and on miniature preview
Between these steps, I of couse always restarted the computer

I want it to look like this:

(for some reason, I have this problem only on my laptop, but not on my desktop pc, even if both are the same Win 10 version, same updates, same Reader version, etc)

Does anyone have an idea how to get rid of that?

Thanks

 

[Irriducibile]

Update: I don't think it should be an Adobe problem because it looks the same with other pdf readers too