By default, $metas will contain all non hidden fields (+ the featured image and the page template). If you want only the custom fields in your array, then you should not merge them to $metas.
add_filter('pll_copy_post_metas', 'copy_post_metas');
function copy_post_metas($metas) {
return array('address','pool_box_check','location','persons','rooms','bathrooms','airport','airport-km','train-km','train','calendar','_secondary_html_128','reference','price');
}