The new block editor uses the REST API and by modifying the rest response through the rest_prepare_post filter you compromise the expected data set. I suspect that’s the case here, since you’re modifying all the responses for the post post type, without any conditional restrictions.
Consider creating your own custom route where you can modify the response to your needs without affecting the core/plugin/app use of the builtin REST API routes. You could also consider e.g. the _embed query parameter to get extra information about the category and the featured image.
Related Posts:
- What hook do I use to edit the post statuses option in admin?
- Modify WordPress Rest Api Request/Response
- How to limit the pages displayed for choosing parent page on page attribute’s menu?
- WordPress Rest filter for custom taxonomy gets applied to the admin area
- Admin post list – adding an option to the date filter dropdown
- WordPress hooks/filters insert before content or after title
- How do filters and hooks really work in PHP
- Trouble understanding apply_filters()
- How to filter users on admin users page by custom meta field?
- Query WP REST API v2 by multiple meta keys
- How many filter/action hooks are healthy?
- Filter specific shortcode output?
- Earliest hook to reliably get $post/$posts
- How to pass/get data to/from the WooCommerce data-product_variations object?
- Where to hook into post content?
- What does (10, 2) mean when used with add_filter
- Clarification on filters and hooks
- Valid characters for actions, hooks and filters
- How to influence the information displayed on widget inside wp-admin
- is it possible to add “extra” table nav to edit-tags.php screens?
- How to hook into unregistering a widget instance?
- How to check if a hook is hooked or not?
- Passing Additional Parameters to add_filter Callable
- Filter hook before create order WooCommerce
- How to add some custom HTML into wordpress admin bar?
- post_mime_types Filter not Working in List Mode
- Custom theme hooks / filters – passing arguments
- wp_mail – Remove sitename from email subject
- How to disable all WordPress emails modularly and programatically?
- How to hook wp_list_pages?
- apply_filters() slices away needed arguments
- WP Rest API – Upload media without saving attachment post
- How to make post and comment count unclickable with dashboard_glance_items hook
- How to use the_excerpt in a filter hook?
- How to add attribute to output with wp_video_shortcode add_filter
- How to change Woocommerce breadcrumbs content?
- Hook into admin post list page
- Anyway to edit the titlebar of WordPress Widgets in the Admin area?
- How can I hide all posts that don’t have a thumbnail?
- Change text of Description in Image Library
- Load different template file when condition met?
- Am I using the right hook for removing quicktags on the admin TinyMCE?
- About Hooks and Filters
- How to enable visual editor when editing comments on the dashboard?
- Should I use add_action(‘publish_post or add_filter(‘publish_post?
- Please explain me what the do_action does
- Is it possible to Hook/Filters Attachment Creation?
- Filter all html output
- Can’t get wp_title filter working in twenty sixteen child theme
- How can I reliably and globally disable wptexturize?
- Customise Jetpack Publicize text
- Removing labels and tag on WordPress’s default login form
- WordPress RSS feed – filter RSS content by custom field value
- user_has_cap filter allows edit but will not allow save
- How to trigger the core WPLANG to make automatically set a language when the theme is activated? [duplicate]
- How to hook some Unicode texts into calendar widget safely?
- How to add attributes to tag when template cannot be directly modified
- filter the_title problem in nav
- How can I register a new REST context?
- How can I add a fifth option to the alignment picker?
- Too many actions/filters!
- Filter the URL of next_posts_link & previous_posts_link
- How to get list of all hooks of current theme / plugin?
- Which hook is fired when inserting media into a post
- Changing Gutenberg / WP block editor width only on pages, not posts or other taxonomies
- How to replace any occurence of Gravatars with a local placeholder image?
- How does WordPress call functions attached to a certain action hook before calling functions attached to other hooks
- Sensei LMS Hooks to Remove Content
- What hook/filter can I use to add/edit/show/hide the title under (on hover) links on the table view?
- Customize user account activation message
- Conditionally call add_action depending on post_type?
- Remove “Get Shortlink” button in admin of custom post type
- Change WordPress RSS link with filter?
- WordPress tag cloud add more links
- Add a header before fields added with the attachment_fields_to_edit() filter
- Error when overriding only some audio shortcode HTML output
- Hide content editor for posts after approriate date
- Why anything done on comments_array hook gets reset?
- Gutenberg disable the “block” tab in right sidebar
- add_filter() function misunderstanding
- Is it possible to track down Actions and Filters?
- When to use actions and when to use filters
- add_filter to ‘woocommerce_before_main_content’ [closed]
- Yoast SEO hooks overriding themselves
- Editing
- Is possible dequeue/remove style from wp_footer() hook and add on wp_head() hook?
- Same Conditionals Not Working on Two Different Hooks
- Filter or Hook to catch pre-rendering of post content
- How to call a function or method that is Namespaced using another plugin
- add filter login_redirect does not contain original requested redirect
- get_header and hook avoid normal call
- Question about how do wordpress filters/actions work
- How to center oEmbedded content
- How to add numeric slug for child page in WordPress 5.9?
- Can the wp_filter object hold multiple values with the same key
- check to see if hook is available
- Change username before login
- How to change the order (priority) of registered filters (or actions) (e.g. for the_content)?
- Add Sortable Column For All Post Types
- apply_filters/do_action tag characters limit