WP Revisionary Preview Wrong Thumbnail Image

post-edit_rvy.php

<?php

public function fltPreviewLink($url, $_post = false) {
    global $post, $revisionary;

    if (!empty($_REQUEST['wp-preview']) && !empty($_post) && !empty($revisionary->last_autosave_id[$_post->ID])) {
        $url = remove_query_arg('_thumbnail_id', $url);
        // EDIT: get thumbnail id instead of setting thumbnail id to autosave post id
        $thumbnailId = get_post_meta($revisionary->last_autosave_id[$_post->ID], '_thumbnail_id', true);
        $url = add_query_arg('_thumbnail_id', $thumbnailId, $url);
    } elseif ($post && rvy_is_revision_status($post->post_status)) {
        $url = rvy_preview_url($post);
    }

    return $url;
}