Adding product to basket in Ubercart causes checkout bug

As part of a site I’ve recently been developing using Ubercart, I needed the ability to be able to add an item to the basket via a URL. Getting a URL to trigger an event was trivial, using the following code. First, you setup the URL pattern to trigger a callback function: Next, I setup a simple callback function, which would get the Node ID from the URL, and pass it to the uc_cart_add_item function and then redirect the user to the checkout. I tried this, and it seemed to work, however I later realised that the delivery pane had…