I am able to create a new post but I get a generic error message
Publishing failed if I try to publish it. Same thing if I try to edit it (or any other post).
If I try to delete the post using the
Move to trash button, I get another error:
The response is not a valid JSON response.
The issue only happens in the new Gutenberg interface (
wp-admin/post.php) I am able to publish or remove the post using the "quick edit" functions on the posts list view (
The problem occurs with all users and for all post types (I tried with posts and pages). Deactivating all plugins and visiting the permalinks page did not solve the issue.