"Page not found" on preview of custom post type with post format

[juanfra]

If you click "Preview Changes" for a custom post type item (with post format), you get 404.

Here is the code to test on any theme's functions.php

if ( ! function_exists( 'my_custom_cpt' ) ) :
add_action( 'init', 'my_custom_cpt' );
/**
 * Add a 'test' custom post type, with a post format.
 *
 * @since eva'
 */
function my_custom_cpt() {
        
        $labels = array(
                'name'                  => __( 'Test', 'textdomain' ),
                'singular_name'         => __( 'Test', 'textdomain' ),
                'add_new'               => __( 'Add New', 'textdomain' ),
                'add_new_item'          => __( 'Add New Test', 'textdomain' ),
                'edit_item'             => __( 'Edit Test', 'textdomain' ),
                'new_item'              => __( 'New Test', 'textdomain' ),
                'view_item'             => __( 'View Test', 'textdomain' ),
                'search_items'          => __( 'Search Test', 'textdomain' ),
                'not_found'             => __( 'No Tests found', 'textdomain' ),
                'not_found_in_trash'    => __( 'No Tests found in Trash', 'textdomain' ),
        );

        $args = array(
                'labels'                => $labels,
                'public'                => true,
                'publicly_queryable'    => true,
                'show_ui'               => true,
                'query_var'             => true,
                'rewrite'               => array( 'slug' => 'test' ),
                'capability_type'       => 'page',
                'hierarchical'          => false,
                'menu_position'         => null,
                'supports'              => array( 'title', 'editor', 'thumbnail', 'page-attributes', 'comments', 'author', 'revisions' )
        );
        
        // register the test post type.
        register_post_type( 'test', $args );
        
        // add post a format
        add_theme_support(
                        'post-formats',
                        array( 'video' )
                );

        add_post_type_support( 'test', 'post-formats' );

} // end my_custom_cpt()

endif;

If you remove the post_format url parameter by hand, you get to see the preview, but not updated. If you do it programatically then you get to see the preview updated.

function remove_post_format_parameter( $url ) {
   
$url = remove_query_arg( 'post_format', $url );
    
   return $url;
}

add_filter( 'preview_post_link', 'remove_post_format_parameter', 9999 );

[DrewAPicture]

#31555 was marked as a duplicate.

[DrewAPicture]

Seems like #20438 could be related to this too, though vicariously.

[chriscct7]

Duplicate of #20438