Hi,
Try to also change the line:
$query->clear() ->select('category_id AS value, category_name AS text') ->from('#__hikashop_category') ->where('category_parent_id IN ('.$filter_value.')') ;
to:
$query->clear() ->select('category_id AS value, category_name AS text') ->from('#__hikashop_category') ->where('category_parent_id IN ('.$filter_value.')') ->order('category_ordering ASC');
Otherwise, I'm afraid it would require proper testing and glancing at your email it looks complex to set that all up to try and reproduce the problem.
Providing support on a custom module we didn't work on is obviously outside what this forum is about.