Updating failed. Error message. The reply is not a valid JSON-reply. Only on index

[Lobsterass]

Hola rockstars!

I just went live with this site and I suddenly get an error message when I try saving changes back-end on the index page. It says: “Updating failed. Error message. The reply is not a valid JSON-reply.” It is possible to save the page front-end though.

I’ve tried to deactivate all new plugins. Still same issue. I don’t have this problem on other pages.

(All I wanna do is just edit the head+meta in Yoast for that page.)

Any ideas?

UPDATE:
I can update index back-end if I activate the “WordPress Classic Editor plugin”. So, I’ve worked around the issue by installing a plug I otherwise don’t need. Is there a conflict between Gutenberg and something else?

UPDATE 2
Classic Editor doesn’t show the images I insert in a blog post front-end, so I had to deactivate it. Initial problem still exists then. Actually, the images uploaded via Gutenberg are now not showing front-end.

[ruenel]

Hello @Lobsterass,

Thanks for writing in!

Have you done a test for plugin conflict? Please allow us to test for a plugin conflict as well. We might need to place your site in under construction mode first and then proceed with the test.

By the way, the feature image is still present. It is hidden by default.

Please let us know how it goes.

[Lobsterass]

Hi!

Yeah, the chosen image for the page is not the problem. I need to have control over open graph features like headline and meta description and I should be able to save any edits back-end without the WP Classic Editor activated.

I still cannot save the index page back-end (due to “Updating failed. Error message. The reply is not a valid JSON-reply.”) with only Gutenberg. In other words, it seems like a conflict between Pro and Gutenberg.

I don’t have this problem on other pages.

Please feel free to put it under construction to check this. Please put it back up when you’re done.

UPDATE regarding the issue of images on the blog, I solved it by installing Really Simple SSL.

[ruenel]

Hello @Lobsterass,

We could not replicate the issue on our local testing servers. This must be unique to your WP installation only. We recommend that you increase your memory allocated to PHP. To increase it, please edit your wp-config.php file and insert these lines:

define( 'WP_MEMORY_LIMIT', '256M' );
define( 'WP_MAX_MEMORY_LIMIT', '512M' );

You can add it before the line
/*That's all, stop editing! Happy Blogging. */

We would loved to know if this has work for you. Thank you.

[Lobsterass]

Hi!

Thanx. It didn’t work though. I don’t know what’s wrong but I got a work around with the WP Classic Editor.

<3

[ruenel]

Hey @Lobsterass,

It’s good to know that you have found a work around to save your changes.

Thanks for letting us know.