Hi,
Sorry for the delay.
I've looked at the issue.
I think that this is a side effect of the code modification I made to better handle orders with 0% taxes.
One of the changes I had made for that was to add the code:
if(isset($tax->amount))
$order->order_tax_info[$tax->tax_namekey]->amount += $tax->amount;
in the file administrator/components/com_hikashop/classes/order.php
This lead to the tax amount containing twice the shipping fee when the order didn't had a 0% tax.
I propose to change that code to:
if(isset($tax->amount) && empty($order->order_tax_info[$tax->tax_namekey]->amount))
$order->order_tax_info[$tax->tax_namekey]->amount = $tax->amount;
That way, it will only set the amount from the shipping if there isn't already an amount. That should hopefully fix the issue for newer orders going forward.
Could you try this out ?