Hi Alessandro,
I checked and this is not caused by the theme or builder, but I couldn’t just continue troubleshooting since it’s a live site. You could try testing for a plugin conflict. You can do this by deactivating all third party plugins, and seeing if the problem remains. If it’s fixed, you’ll know a plugin caused the problem, and you can narrow down which one by reactivating them one at a time.
Then please provide your FTP login credentials in the secure note and I’ll disable the plugins through there. In case I need to disable them while troubleshooting.
Let us know how it goes!