Even if the casino claims it's a bug and refunds the gamblers' bets, there's still some damage done. That's why it's justifiable for the regulator to fine them.
Yes, there's damage done, complete waste of the customers' time, one they could have used to play in a different platform or another game in the same platform, at least with a chance of winning something. The $19,000 fine and the $3,500 for White Hat is fair and it should stand as a deterrent to other platforms, to make sure they check their systems regularly for bugs, especially one of this kind that can hurt their reputation in the industry and make them lose customers.