Sites are empty in the Backend

I have the Problem that I cant edit some existing sites in the backend. The content area is empty. But the website is still online and everything is fine. Its just a problem with the content in the backend. I tried to create a new site and copied some text in the content area. However after I saved it Its not displayed at the website.

Is there some problem with a new version of wordpress and the theme? I hope someone can help me. Thanks.

Hello there,

Check out this codex that might help you find out what’s causing you such that issue.

Does it also happen when you compose a new page or post?