Hi @Regnalf,
It will be very difficult to understand what is the reason behind your issue, I would suggest you troubleshoot the following common issues to recognize the problem.
1.Theme Related Issue
2.Plugin Conflict
3.Theme Update related issue
4.Child Theme Related issue ** If you have activated it
If you discover that an issue is coming from a custom code or 3rd party plugin, kindly consult with a developer or contact the plugin author. Please note that we do not provide support for custom codes and 3rd party plugins.
Please also check if that the issue is coming from the Custom Post Type code. Please remember that Custom Post Type related issues are beyond the scope of theme support.
If none of the above helps and you are still getting the issue, please provide login credentials for your site in a secure note to examine it further, including:
– WordPress Site URL & Login URL
– WordPress Admin username/password
To create a secure note, click the key icon underneath any of your posts.
Thanks