Shipping calculator resets

Store URL: https://www.watersave.com.au/uridan-waterless-urinals/uridan-consumables-store
WordPress version: 3.6.1
WP e-Commerce version: 3.8.12.1
Gold Cart version: 2.9.7.6
Theme: Custom theme

I did this: Selected shipping state. Calculator updates to correct price. Ticked “Same as billing address” checkbox. Shipping cost now resets, requiring the state field in the calculator be selected again.

I expected WP e-Commerce to do this: Select shipping state and calculate the shipping price. Ticking “Same as billing address” should either update the calculator to the billing state or not affect it at all.

Instead it did this: Resets the shipping calculator. Prevents checkout until the calculator redoes the shipping cost.

Steps to reproduce:
1. Add any product to cart from https://www.watersave.com.au/uridan-waterless-urinals/uridan-consumables-store
2. Click the Checkout button.
3. Select a state in the shipping calculator.
4. Scroll down to the “Shipping Address” area and tick “Same as billing address”.
5. A loading animation appears and disappears. The shipping price may change.
6. Scroll back up to the top of the page and you’ll see the shipping calculator has been undone.

Previously this issue was resolved with a premium support token (post-310483) where they uploaded a beta release of WPEC to resolve the issue.

https://www.ads-software.com/plugins/wp-e-commerce/