Repeatable group data not in REST response

Hi,

I'm trying to use meta-box to create an interface for data that will be returned by the REST API. I have the MB Rest API and Meta Box Group plugins installed.

I have the following definition for data fields:

add_filter( 'rwmb_meta_boxes', 'your_prefix_function_name' );

function your_prefix_function_name( $meta_boxes ) {
    $prefix = '';

    $meta_boxes[] = [
        'title'      => __( 'Nav page', 'your-text-domain' ),
        'id'         => 'nav-page',
        'post_types' => ['page'],
        'fields'     => [
            [
                'name'   => __( 'Group', 'your-text-domain' ),
                'id'     => $prefix . 'group_mja12hpcr0h',
                'type'   => 'group',
                'clone'  => true,
                'fields' => [
                    [
                        'name' => __( 'Name', 'your-text-domain' ),
                        'id'   => $prefix . 'name',
                        'type' => 'text',
                    ],
                    [
                        'name' => __( 'Relative url', 'your-text-domain' ),
                        'id'   => $prefix . 'url_b4fovvhcvnb',
                        'type' => 'text',
                    ],
                    [
                        'name' => __( 'Icon', 'your-text-domain' ),
                        'id'   => $prefix . 'icon_fa',
                        'type' => 'text',
                    ],
                ],
            ],
        ],
    ];

    return $meta_boxes;
}

After adding data to a couple of these groups, in the REST response I only see this:

        "meta_box": {
            "group_mja12hpcr0h": []
        },

How do I get this to work?