Image showing on page with metaslider even after excluding

Hi,

On a site where we’ve setup the Default Featured Image plugin. Its working fine except where the front page uses Metaslider. Even after excluding the page using the code below in the functions file:

add_filter( 'dfi_thumbnail_id', 'dfi_skip_page', 10, 2 );
function dfi_skip_page( $dfi_id, $post_id ) {
    if ( $post_id == 23 ) {
        return 0; // invalid id.
    }

    return $dfi_id; // the original featured image id.
}

Page id is 9 and code changed to $post_id == 9. It still shows the image and seems to stutter before the slideshow begins.

Is there anything else that needs to be done?