It seems that scammers are getting away with your money. With a solid proof, I think that you can reject a withdrawal as long as you made it on public like posting it in this thread or somehow a scam thread against this casino. Scammers are really creative and silly nowadays, They try will try to abuse your casino as long as you are still paying and haven't questioned anyone. Remember that there are people who can sold their identities in the streets for some cheap alcohols. This is why sometimes even KYC is not enough in detecting people in abusing a casino. Two or more accounts logging-in in a same phone is a solid red flag and a big proof that they are scammers.
I think people should be more careful with their words when they make something public. Calling someone a scammer just based on an innuendo posted by a third party is very unprofessional unless that person also works for the same casino or is an apologist for it. I see that a lot of people who post here have a casino banner in their signature, so I assume that they are somehow biased and not credible enough in justifying any casino.
I have been playing in casinos for over 20 years, I love playing blackjack. I'm sure I've played over a million hands of blackjack in my life and when I read some of the posts here I can only laugh. A representative of this casino says that some players cheated or manipulated the third-party blackjack game (Relax gaming). If only I knew how it could be done! Would we rather talk about the very strange results of a house blackjack game than blackjack.fun? As I mentioned, I've been playing blackjack for a very long time and I've almost never seen streaks in my life that are weirder than on house blackjack than blackjack.fun and can someone explain to me how it's possible for a rollercoaster of 200-300 stakes to happen on a daily basis ? And don't talk to me about proven fair play because that doesn't prove anything. Last hand played fair? OK, and what about long-term statistics? Are the long-term statistics fair, can you prove it and where can it be checked? Or do players simply have to take your word for it and the work of your developer? Here I will give my subjective comparison between Relax blackjack and house blackjack: the two games have absolutely no similarities, and both games are called blackjack. If I wanted to trick someone, then I would program blackjack the way blackjack.fun did it
I advertised your casino in a private forum in my country (Croatia). It is a very small forum of people (there are about 30-40 of us) who love gambling and where we exchange information and experiences, exactly like the players do on the bitcointalk forum, only there are very few of us. Some of us know each other personally because only in our capital city lives about 25% of the total population of the country. And the OP says all the accounts (or most) are from the same location. That's weird, isn't it? And funny.
According to my information (after writing about this case on our forum) only 4 or 5 people from our forum registered on blackjack.fun and played regularly. And it is not true that the accounts were opened one after the other after one account was played and a payout was made. Several members of our forum confirmed to me that they played at the same time, and also continued to play after the bonus was paid, so the OP's information that the accounts were closed after the bonus was paid and then new accounts were opened is not correct.
The OP says that a gang from Croatia systematically attacked casino blackjack.fun and took advantage of the benefits. After all these years of gambling it sounds like a kid's joke to me. Casino offers a promotion to attract new users. The casino is aware and knows that the player has a mathematical advantage in that promotion, and after a few new people register and accept the bonus, then the casino declares these people abusers?
Question for the OP: after how many new registrations from a certain country or the same city does the casino start banning players, confiscating their money and declaring them fraudsters? One or two? I am asking this because I have a good reputation on our forum and after these negative experiences with some of our users in your casino I am very sorry for recommending and advertising you because it seems that no one is allowed to register in your casino anymore and request any what kind of promotion or bonus.
Maybe one of our local forum users tried to do a scam in the sense that he opened two accounts from the same device, I can't know and I condemn it. If you have evidence for such acts, then everything is clear, but if you only have information that some users know each other and that they are from the same city or country, this cannot be any evidence of fraud, and in this way, the players you suspect are harmed because they are innocent .
Finally, I think it should be clear to everyone that there is a risk of losing money by entering a casino. But casino owners must also be aware of this because it is not a one-way street...