Wordpress and Polylang: prevent certain custom fields' values from synchronising between posts in different languages (they always sync by default)

polylang.php

<?php
// We could use wpml-config.xml to turn off the sync, but it wouldn't support repeater-like fields
function themeprefix_dont_sync_specific_fields( $metas ) {
  $unsync = array(
    'office_country',
    'uspage_liftups_repeater'
  );
  
  // Support for repeaters, flexible content fields etc.
  if ( is_array( $metas ) && is_array( $unsync ) ) {
    // loop over all passed metas
    foreach ( $metas as $key => $value ) {
      // loop over each unsynced item
      foreach ( $unsync as $find ) {
        if ( strpos( $value, $find ) !== false ) {
          unset( $metas[$key] );
        }
      }
    }
  }

  return $metas;
}

add_filter( 'pll_copy_post_metas', 'themeprefix_dont_sync_specific_fields' );