Hi,
Ok, now I see your issue.
The "custom field" filter accept the "none" value but the manufacturer does not accept the empty value while submitting something.
In the filter class (file : administrator/components/com_hikashop/classes/filter.php ) please replace
if($filter->filter_deletable && $selected[0] != $filter->filter_namekey && $selected[0]!='none' && ( isset($selected[0]) && !in_array($selected[0],array(" ",'')))){
[code]
By
[code]
if($filter->filter_deletable && $selected[0] != $filter->filter_namekey && $selected[0] != ('filter_'.$filter->filter_namekey) && $selected[0]!='none' && ( isset($selected[0]) && !in_array($selected[0],array(" ",'')))){
It would fix your problem.
Regards,