Checkout delivery details continue button not working

Hello,

I am on OC version 2.0.3.1 and using the "Journal Theme".

I've not ran into this issue before now, but recently I started getting complaints from customers that they could not add a separate shipping address to their billing address. On inspection it appears that when pressing the continue button after entering delivery details, it changes to loading, then just resets and nothing happens. I can't seem to find a solution to this problem anywhere, I would try updating my OC version but someone worked on my website and I believe they may have changed some of the OC files which I don't want to replace.

The website in question is www.huggableheroes.co.uk

Any suggestions or help would be greatly appreciated. If you need more information I can provide it, but I'm not good with JS or PHP.

Thank you,

Dan