Update, the withdrawal went though and has now been sent to pending.
I did a 500x hit on the slots.
I guess mintdice is processing all the transactions manually,so worth to wait for that 500x reward.Picking up the high priority fee will make things much faster!
I think manually is a common concept in casinos, there has been a lot of people who have abused the automatic system with the double spending method of nonconfirmation with zero fee etc etc which goes back to the sender because the fee is not enough and it is not getting picked up by the blocks.
It means if casinos let the automated withdraw work, they would see the money coming in and then they would credit the gambler and if they lose they get their money back anyway, if they win they both get their money back plus the wins. Hence the automated system doesn't really work anymore, maybe if the confirmation process takes longer, like takes 3 confirmations to get credits but that would mean gambler can't gamble right away and their gambling hype may die.
What you're describing is called double spending.
It can happen if a blockchain forks/splits into two chains for a little time before one of the two chains becomes invalid, usually because an entity takes over 50% of the consensus of the network.
This is something every unlikely to happen with Bitcoin.
Also if a transaction is canceled because it was sent with too low fees, then it has never been confirmed and there's no reason any company would credit you the amount of an unconfirmed transaction.