Hello everyone,
we have the following problem:
I am creating a new page and using the “Blank Page” preset.
Then I can enter the text and save this page.
As soon as this page is created, the entire text is gone and I have to add it afterwards through editing.
Does anyone have the same problem or a tip on what might be causing this?
push. 
No idea, never seen this. You’d need to explain how you installed XWiki, your configuration and how to reproduce it.
Maybe check the javascript console to see if there are any errors when you click “save” and when the page content is not saved.
I never met with this kind of issue.
I would suggest several things such as trying another web browser, checking if web browser is up to date, try several browsers (ie : Firefox, Chromium, Chrome, Edge, Brave, Opera), provide names and versions of the web browsers tested, empty the browser cache and cookies.
I would also suggest checking if the XWiki instance is up to date : as well on the server side as on the website extensions. (And provide context in forum posts, such as what is the XWiki server, Docker or else, and what version).
Im very sorry for the late reply!
The update to 16.6.0 has fixed the issue.
Thank you for your efforts!