Anchor not saving

Love this extension. Great job!

While working with it, I noticed that the anchor does not save and is not available through the callback attribute.

Here is a snippet of my code:

$meta_boxes[] = array(
                'id'         => 'twt-gallery-block',
                'title'      => 'TWT Gallery',
                'type'            => 'block',
                'icon'            => 'layout',
                'category'        => 'layout',
                'render_callback' => array($this, 'render_block'),
                'supports' => array(
                    'anchor' => true,
                    'customClassName' => true,
                ),
                'fields' => array(
                    array(
                        'name' => 'Images',
                        'id'   => 'images',
                        'type' => 'image_advanced',
                    ),
                    array(
                        'name' => 'Row Height (px)',
                        'placeholder' => '300',
                        'id'   => 'row_height',
                        'type' => 'number',
                    ),
                    array(
                        'name' => 'Displayed At Start',
                        'placeholder' => '20',
                        'id'   => 'displayed_at_start',
                        'type' => 'number',
                    ),
                    array(
                        'name' => 'Load More Increments',
                        'placeholder' => '10',
                        'id'   => 'load_more_increments',
                        'type' => 'number',
                    ),
                    array(
                        'name' => 'Last Row',
                        'id'   => 'last_row',
                        'type' => 'select',
                        'options' => array(
                            'justify' => 'justify',
                            'nojustify' => 'don\'t justify'
                        )
                    ),
                )
            );

Not urgent…