Hey @Dario,
Thanks for reaching out. I checked out your site, but did not find any different behavior whether I refreshed, AJAX searched, etc.
All I saw, no matter what I tried, was the design shown in this screenshot:

1. ☝️ Is that an example of when the CSS does not load?
2. Can you share screenshots of what you see? You can do so by uploading the screenshots to this thread. If you have issues with that, you can upload to Imgur.com, Flickr.com, CloudUp.com, or any similar image-hosting site; then just share the links to those images here and I’ll take a look.
3. Can you please post your site’s “System Information” to this thread? Here’s how ? https://theeventscalendar.com/knowledgebase/sharing-sys-info/
Thanks!
George