PayPal Adv. doesn't consistently go to the iframe

m2820.com
Joomla: 2.5.20
HikaShop: 2.3.1
PHP: 5.4

Here's what happens: If you add an item to the shopping cart > click "Proceed to checkout" > Register and add your address > Choose payment method > Click "Finish" > then instead of proceeding to the PayPal iframe where you enter your credit card information and pay, instead, the plugin takes you to the web address that I place inside the field Configuration>Cart: "URL where to redirect when the cart is empty." So, it seems that the cart is being emptied before I get to the iframe page, so it is redirected.

However, after you are redirected, the item is still in the shopping cart, so if you click, "Proceed to checkout" a second time, and go through the same process a second time, it will take you to the last screen where you can enter your credit card information.

Now, the above error occurs for the following Checkout Workflow:

Alright, so I may have fixed the problem.

After changing the Checkout Workflow flow to something else, the checkout process worked correctly. So, I started trying different Checkout flows, changing the elements around to try to figure out what order caused it to break. Several Checkout Workflows orders worked, so I decided to put it back the way I originally had it, and it still worked.

So, now it works, but I'm not sure why since the only thing that changed was changing the Checkout Workflow to something else, then changing it back.