FOUND THE PROBLEM
Actually, I was exporting via JSON anding using R::exportAll( arrayResult ) to convert all objects to JSON
I changed the way to export the data and it was fixed.
$o = R::load("page", 1)->ownItemList;
$all = R::exportAll($o);
return json_encode( $all );
NOW:
$all = array();
$o = R::load("page", 1)->ownItemList;
foreach($o as $k => $v) {
array_push($all, $v->export());
}
return json_encode($all);