Some Media page permalinks don't work

Hello! Sorry, I’m at my first-time of wordpress site.
It is in
https://www.kitesurfcorsi.it/prova
I set the permalinks as /% postname% and I have installed the plugin ESB Extension URL. I have set up it as .html to get google friendly URLs.
The pages and articles are all ok, but in the media’s pages (images only) some permalinks just work, others many do not work, they give 404 Oops, This Page Could Not Be Found! even though I disconnected and reconnected them to the correct page. What can I do ’cause they all work?
Thanks!