Aggregate shipping costs

Love the plugin and impressed by the flexibility. However I came across a problem today when a customer bought two items. Most of my customers buy one product. Previous to installing the plugin, I had Woocommerce set up to aggregate the individual shipping costs ie the sum of the shipping cost for each line item in the basket.
Today this customer ordered two items viz Product 1 and Product 2. If he had ordered these previously he would have paid the aggregate of the two shipping costs but as you will see from the image he was presented with an option of paying the aggregate or the shipping cost for only one. Naturally, he chose the lower cost
https://snipboard.io/WyfiaZ.jpg
Is there a way to stop this happening?

The page I need help with: [log in to see the link]