Mael

You won’t be able to do that. If the thmbnail does not generate, save the file localy and rename it.

Ok. This happen because of Wikimedia fiole name rewriting.
Wordpress can’t handle names with all those “_%/” instead of “_”.

It’s not the URL of the image, it’s the one of the page where the image is located.
Try a right click on the image, you should have “Copy Image URL” On Chrome or Firefox.

I remember having this problem before, after an other upgrade of WP.
I guess it’s because of jQuery version.