I just updated from 3.28.0 where everything was fine to 3.29.4 and basically everything is broken now.
The thumbnails in the panel won't load any more:
Worse than that: The gallery previews won't load either:
also the pictures wont load:
When I click the link in the error message I get:
Howerver, when I click on the image link which supposedly doesn't exist, the image is displayed by the browser. So It does exist and is accessible.