I have changed the field name to field key in my “get rating fields” function:
function get_comment_rating_fields($group_id) {
$rating = acf_get_fields($group_id);
$rating_fields = array();
foreach ($rating as $item) {
$rating_fields[] = array(
'field_label' => $item['label'],
'field_name' => $item['key'],
'field_min' => $item['min'],
'field_max' => $item['max']
);
}
return $rating_fields;
}

and everything is fine now!
