Yep, we're sorry about this, but at this time there isn't much we can do. We are trying to sort it out with the payment provider, as a lot of people have been having this issue, and we are fully aware as to how frustrating and inconvenient it is Thanks for the feedback, I've bought the game anyway ...

Had the same issue yesterday, my VISA card was correctly debited (the bank has received the authorization), but I got the (unknown) error with Braintree.
This mean the amount of 20€ is blocked from my bank account as long as the payment authorization is valid (7 to 10 days)...