Hey @Bor,
The issue could possibly stem from incorrect WordPress setup. We need to know if X is causing this so the first thing that you need to do is to backup your site. Then, switch to the default WordPress theme and test your form again. If the issue persists, you need to contact the Contact Form 7 support because they are the specialist when it comes to their plugin and also, we don’t have support for third party plugins although CF7 is an approved plugin.
If the issue is fixed, please give us WP admin and FTP access in a Secure Note.
Thanks.