First of all, I have never experienced such a situation, and I have never heard of gamblers in crypto gambling casinos refunding a gambler's fund or the jackpot won by gambling on their platform.
But as you said, in such situations, a casino can really refuse to give it, especially since the refund is a large amount requested. If that's the case, of course you have to try to contact the casino's support to find out their answer to the refund you want to happen.
How possibility with casino know about bug on their system? I think when success winning huge amount in casino gambling platform as soon possible take withdraw without confirming from casino with how much winning fund. Usually experience casino never have weakness side exactly get bug most of casino have good their game play and less possibility for user winning much amount.
I don't see any cases with casino ask the refund when user winning huge amount, keep silent if there are have small bug with casino platform and withdraw its small by small fund without make casino detected with our withdrawing huge amount in once time. Never have cases when winning jack pot in casino platform are bug or mistake from their site because its our winning.
If I am not mistaken, I've read that some casinos refund their gamblers because of errors or bugs that occur in the casino, but I forget which casino. The casino gave refunds to gamblers who made deposits or withdrawals or something other than that, I really can't remember.
But in general, casinos can give rewards to gamblers who find bugs. But if gamblers experience losses due to bugs occurring in the casino, perhaps the casino will give a refund to the gambler, especially if they can provide proof to the casino.
But if someone managed to win the jackpot prize and the casino couldn't award the prize because they accused the gambler of cheating, that would look suspicious because the gambler clearly could have won the jackpot.
Perhaps the casino needs to investigate before they give out the jackpot prize.
It is the duty of a casino that has errors, because it must make refunds, although very few casinos are honest and say that they have had an error with the clients, generally the errors are in favor of the casino, they correct them and do not say anything , but when they are errors where the client wins and does not know that it is a bug then that money stays there, and sometimes it seems a little unfair because it lends itself to misunderstandings, they can say that the casino manipulated the results to not pay the player, So in these cases it is always better that the casino pays for the error, because that can lead to misunderstandings and make things look bad, with a topic that is launched by the Reputation part in the forum is enough to form a problem and it is very rare to say that the player made a mistake precisely when the player was playing, because it is vain to say that the games are only programmed to make people lose.
I don't remember which casino it happened in because they didn't realize the error, what they did was generate massive closures of withdrawals and they didn't let anyone withdraw while they fixed the problem, but I think that later there were many complaints, in the first instance the person It feels bad, because if it is something who feels that they were lucky and then they took everything away from them, it is not a good thing. In fact, as I said before, the duty of a casino is to pay, but when the problem is the opposite, well It is difficult for a casino to accept that there was an error and they have to replace that money, unless they have casinos like stake.co, bitcasino.io which are really casinos that are always at the forefront and that do everything they can to be the best , they will not start fighting with any co-player in truth, things were fair as I say, but why? Because they are old casinos, with a very high reputation, with enormous trust, where they only care about the well-being of their players.