Gutenberg: Error while saving (The JSON-Answer is not a valid answer

This may be a plugin or theme conflict. Please attempt to disable all plugins, and switch to the default Twenty Twenty theme. If the problem goes away, enable them one by one to identify the source of the problem.

If you can install plugins, install Health Check. On the troubleshooting tab, you can click the button to disable all plugins and change the theme for you, while you’re still logged in, without affecting normal visitors to your site.

Sorry for my late answer,

Just checked it again. It’s kinda weird…
If the lenght of the page is shortend, it’s working without any Problems, so it has to be the lenght. Do you know if there is a limit?

I will test the Plugin Health Check. Thanks for your help!

EDIT: After aktivating that Plugin, when all Plugins are deactivated and the Theme is the basic one, the error still occurs.

• This reply was modified 4 years, 11 months ago by wi_VOID.

There is no character limit that we know of.

Try downloading WordPress again, access your server via SFTP or FTP, or a file manager in your hosting account’s control panel (consult your hosting provider’s documentation for specifics on these), and delete then replace your copies of everything on the server except the wp-config.php file and the /wp-content/ directory with fresh copies from the download. This will effectively replace all of your core files without damaging your content and settings.

Some uploaders tend to be unreliable when overwriting files, so don’t forget to delete the original files before replacing them.

Ok i jsut did that. Still the same error…
Any other idea?

UPDATE: Now it’s even worse. Now actually every page is failing, like the one.

• This reply was modified 4 years, 11 months ago by wi_VOID.

Ok, please make sure that your browser is up to date: https://browsehappy.com/

If it is not, please try updating your browser or switching to a different browser.

If it is, please do these two things:

1. Try clearing your browser’s cache and cookies.

2. Try with all browser extensions or add-ons temporarily disabled.

Please let us know how each step goes for you, and which browser (and version of) you’re using if you’re still having trouble.

Tried that already, too.

I tried:
– Firefox: 70.0.1
– Google Chrome: 79.0.3945.88
– Safari: Can’t look it up right now.

I deleted the cache from all 3 (different PC’s). Still same error.

How about Firefox 71?

Still not working.

What version of PHP are you running, and who is your hosting provider?

Sorry for my late answer.

PHP: 7.3 (Tried already changing to 7.4 -> still same error)
Hosting: Strato

Hm, ok, are you also running the Gutenberg plugin? The editor is built-in now, the plugin is just a testing ground for new features and bug fixes.

If so, any improvement with it off?

If not, any improvement with it on?

I just installed and activated it.
– No Improvement

Are you running any server-side security, like mod_security or a firewall, or a security reverse-proxy, like Cloudflare or Sucuri?

If so, would you please try with those off?

I think i do not have one. But I’m not quite sure…
If I’m only have my provider, usually i do not have one or do I?

You can check with your hosting provider’s support, they’ll let you know.