wp not making CPT permalink / slugs unique

Question

I've registered a custom post type on my site but loads of different users are able to create posts with the same slug / permalink, here is how I am registering my post type

// Bucket Custom Post Type
function bucket_init() {
// set up bucket labels
$labels = array(
    'name' => 'Buckets',
    'singular_name' => 'Bucket',
    'add_new' => 'Add New Bucket',
    'add_new_item' => 'Add New Bucket',
    'edit_item' => 'Edit Bucket',
    'new_item' => 'New Bucket',
    'all_items' => 'All Buckets',
    'view_item' => 'View Bucket',
    'search_items' => 'Search Buckets',
    'not_found' =>  'No Buckets Found',
    'not_found_in_trash' => 'No Buckets found in Trash', 
    'parent_item_colon' => '',
    'menu_name' => 'Buckets',
);

// register post type
$args = array(
    'labels' => $labels,
    'public' => true,
    'has_archive' => false,
    'show_ui' => true,
    'capability_type' => 'post',
    'hierarchical' => true,
    'rewrite' => array('slug' => 'bucket'),
    'query_var' => true,
    'menu_icon' => 'dashicons-editor-bold',
    'menu_position' => 20,
    'taxonomies' => array('category', 'post_tag') ,
    'supports' => array(
        'title',
        'editor',
        'excerpt',
        'trackbacks',
        'custom-fields',
        'comments',
        'revisions',
        'thumbnail',
        'author',
        'page-attributes'
    )
);

register_post_type( 'bucket', $args );

}
 add_action( 'init', 'bucket_init' );




  /**
 * Hooks the WP cpt_post_types filter 
 *
 * @param array $post_types An array of post type names that the     templates be used by
 * @return array The array of post type names that the templates be     used by
 **/
function my_cpt_post_types( $post_types ) {
$post_types[] = 'bucket';
$post_types[] = 'actor';
return $post_types;
}
add_filter( 'cpt_post_types', 'my_cpt_post_types' );

So if a user creates a post called hello, and another creates a post with same name it doesn't add a unique number after for example; hello-2. Is there a way I can easily do this..

Or ideally.. Can I set it just be post id instead?

This post type goes 3 levels deep, here is it in action:

http://buckets.me/bucket/sri-lanka-planning/guides/luxe-guide

So a user can create a bucket, then a folder, then a resource.

I have over 400 users sign up in one day, so whatever I change needs to resolve all existing posts without there being any issues.

Thanks