In saparcelplus.php, if you leave the checkout page and then return, the shipping is
recalculated and insurance is charged on the shipping (making your shipping cost higher).

To fix this bug, modify saparcelplus.php as follows:

Around line 134, replace this line:
global $order, $shipping_weight;
with this line:
global $order, $cart, $shipping_weight;

Around line 163, replace this line:
$order_total = $order->info['total'];
with this line:
$order_total = $cart->show_total();


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