Hello,
To add that fix through your test website, you'll just have to edit the following file "\administrator\components\com_hikashop\helpers\shippingplugin.php" and add these lines :
$implode_product_ids = implode(',', $product_ids);
if(empty($product_ids) || empty($implode_product_ids))
continue;
just after these lines :
foreach($order->shipping_prices as $key => $shipping_price) {
if(empty($shipping_price->price_per_product) || empty($shipping_price->products))
continue;
$shipping_ids = array_keys($shipping_price->price_per_product);
hikashop_toInteger($shipping_ids);
$product_ids = array_keys($shipping_price->products);
The problem seemed to be coming from the fact that your customers had a product in his cart which wasn't available anymore (deleted / unpublished / ...) so the system was trying to automatically estimate the shipping price without having any information about a cart product.
Kind regards,
Mohamed.