ACF, CPT, WP Query | Type: PHPCPT to CPT Reverse Query

Reverse query from different post types associated via ACF relationship field.

Offices

<?php
$offices = get_posts(array(
    'post_type' => 'office',//other post type we're getting data from
    'meta_query' => array(
        array(
            'key' => 'personnel', //name of custom field from above post type
            'value' => '"'.get_the_ID().'"'.
            'compare' => 'LIKE'
        )
    )
));
if( $offices ):
    foreach( $offices as $office ):
        Do stuff
    endforeach;
endif;
?>

Reference Links

https://www.advancedcustomfields.com/resources/querying-relationship-fields/