Nested Clones Break

Hi,

I have created a group of inputs that are clonable and within this group there is another clonable input. I can only see the nested cloneable inputs add button but I can see the parent one for the group in the html given the display none style.

Neither have reached there maximum clones specified. Any ideas?

array(
            'name'   => 'Create Feature Banners', 
            'id'     => $prefix .'home_banner_features',
            'type'   => 'group',
            'clone'  => true,
            'max_clone' => 2,
            'sort_clone' => true,
            'add_button' => 'Add Bannner',

            	'fields' => array (
		            array(
		                'name'  => 'Banner Title',
		                'desc'  => 'Enter title for banner',
		                'id'    => $prefix . 'feature_banner_title',
		                'type'  => 'text',
		                'size'  => 60,
		            ),
		            array(
		                'name'  => 'Banner Description',
		                'desc'  => 'Enter description text for banner',
		                'id'    => $prefix . 'feature_banner_desc',
		                'type'  => 'textarea',
		            ),
		            array(
		                'name'  => 'Banner Background Image',
		                'desc'  => 'Select an image for the background',
		                'id'    => $prefix . 'feature_banner_bg',
		                'type'  => 'file_input',
		                'max_file_uploads' => 1,
		            ),
		            array(
					    'name'        => 'Banner links/buttons',
					    'id'          => $prefix .'feature_banner_links',
					    'type'        => 'post',
					    'clone'		  => true,
					    'max_clone'   => 4,
					    'add_button'  => 'Add Button',
					    'sort_clone'  => 'true',
					    // Post type.
					    'post_type'   => array('page', 'post','event', 'course'),
					    // Field type.
					    'field_type'  => 'select_advanced',
					    // Placeholder, inherited from <code>select_advanced</code> field.
					    'placeholder' => 'Select an item to link',
					    // Query arguments. See https://codex.wordpress.org/Class_Reference/WP_Query
					    'query_args'  => array(
					        'post_status'    => 'publish',
					        'posts_per_page' => - 1,
					    )
					)
				)
			)

Here is the code in question.