[UIXPress] Media library isn't displaying images

I have a very annoying bug that I encounter on all my UIXPress sites (regardless of the theme or plugins). The media library no longer displays, or rather, the media images, whether in the back office or directly in Gutenberg when I edit the site and search for media.

This problem appears when the UIXPress "New Modern Media Library" feature is not enabled, even if I disable the theme for the user (see screenshot).

Could you take a look at it or tell me how to fix it? It's a major obstacle.

Thanks !