multicheck options question

Hi,
first of all thanks so much for your plugin!
I love it!

I have an issue which I don’t seem to understand,
I need to build an option array for a multi checkbox,
this array is made out of a wp_query

Here is the code:

/*
* initie metaboxes
*/

add_action( 'cmb2_init', 'cmb2_ratchet_metaboxes' );
/**
 * Define the metabox and field configurations.
 */
function cmb2_ratchet_metaboxes() {

    // Start with an underscore to hide fields from custom fields list
    $prefix = '_cmb_';

/**
     * Initiate the metabox for Works
     */
    $cmb = new_cmb2_box( array(
        'id'            => 'works_details',
        'title'         => __( 'Work Details', 'cmb2' ),
        'object_types'  => array( 'work', ), // Post type
        'context'       => 'normal',
        'priority'      => 'high',
        'show_names'    => true, // Show field names on the left
        // 'cmb_styles' => false, // false to disable the CMB stylesheet
        // 'closed'     => true, // Keep the metabox closed by default
    ) );

	$cmb->add_field( array(
        'name'       => __( 'Work main image', 'cmb2' ),
        'desc'       => __( 'Work main image, dimensions: 1920px x 380px', 'cmb2' ),
        'id'         => $prefix . 'work_main_img',
        'type' => 'file',
    ) );

	/*custom query to build multicheckbox options*/
	$clientsArray = array();
	$subs = new WP_Query( array(  'post_type' => 'client', 'orderby' => 'date','posts_per_page'=>'-1' ));
	if( $subs->have_posts() ) : while( $subs->have_posts() ) : $subs->the_post();
	$postid = $post->ID;
	$title = get_the_title( $postid );
	$clientsArray[$postid] = $title;
	endwhile;
	endif; wp_reset_postdata();

	$cmb->add_field( array(
		'name'    => __( 'Clients', 'cmb2' ),
		'desc'    => __( 'check clients (optional)', 'cmb2' ),
		'id'      => $prefix . 'multicheckbox_clients',
		'type'    => 'multicheck',
		//'multiple' => true, // Store values in individual rows
		'options' => $clientsArray,
		'inline'  => true, // Toggles display to inline
	) );
}

The problem is at the very end,
$clientsArray is not recognised,
when I print_r it it gives:
Array ( [27] => Argos [26] => Google )

When I switch and enter manually the options:

'options' => Array ( 27 => 'Argos', 26 => 'Google' ),

It works like a charm,

I don’t know what I’m missing,
but if you could help that would be great!

Thank you!

https://wordpress.org/plugins/cmb2/