First item in Group field not being saved

I have a group field and the first item isn't being saved. I have used group several times and it's the first time I've seen this issue. This is my field definition:

    $meta_boxes[] = array(
        'title' => __('Sidebar Content', 'slsh-admin'),
        'context' => 'normal',
        'priority' => 'high',
        'post_types' => array('job-opportunity'),
        'fields' => array(
            array(
                'id' => 'position-details',
                'type' => 'group',
                'add_button' => 'Add a Detail +',
                'clone' => true,
                'sort_clone' => true,
                'fields' => array(
                    array(
                        'id' => 'label',
                        'name' => __('Label', 'slsh-admin'),
                        'desc' => __('e.g. Location, Salary, Start Date', 'slsh-admin'),
                        'type' => 'text'
                    ),
                    array(
                        'id' => 'value',
                        'name' => __('Value', 'slsh-admin'),
                        'desc' => __('e.g. Hamilton, ON; 50,000-60,000 a year; Jan 1, 2000', 'slsh-admin'),
                        'type' => 'text'
                    )
                )
            )
        )
    );

And my data is being saved like this:

a:2:{i:0;a:2:{s:5:"label";s:10:"Start Date";s:5:"value";s:11:"Jan 1, 2027";}i:1;a:2:{s:5:"label";s:8:"Schedule";s:5:"value";s:15:"Mon-Fri 9am-5pm";}}

There should be one more item in my field value.