wp-rm-duplicate-terms.php

<ol>
<?php

/* Remove duplicate meta, in this case Author and Contact (custom tax) */
// Get all posts assigned a term in a specific custom taxonomy.
$tax = 'contact';
$args = array(
    'post_type' => 'post',
    'posts_per_page' => 1000,
    'orderby' => 'ID',
    'tax_query' => array(
        array(
            'taxonomy' => $tax,
            'operator' => 'EXISTS',
        ),
    ),
);
$query = new WP_Query( $args );

foreach ( $query->posts as $post ) {
    $rm_term    = ''; // Var for result of wp_remove_object_terms().
    $post_id    = $post->ID;
    $author_id  = $post->post_author;
    // Get post term.
    $post_terms   = wp_get_post_terms( $post_id, $tax, array( 'fields' => 'ids' ) );
    // Get term meta holding User ID.  
    $term_user_id = get_term_meta( $post_terms[0], 'user_id', true ); // CF with user ID of contact.

    // If Author is also the Contact.
    if ( $author_id == $term_user_id ) {
        // Uncomment to remove term.
        // $rm_term = wp_remove_object_terms( $post_id, $post_terms[0], 'contact' );
        // List results.
        echo "<li>$post_id  /  $author_id / $term_user_id / $rm_term</li>";
    }
}

wp_reset_postdata();
?>
</ol>