Mostly i was scammed by casino in two ways. Lots of KYC requirements with long expectation and "we have suspicions of a fixed match". It is enough for any casino. With fixed matches it is funny enough. One casino pay, the other one freeze money for 24 hours, the another one says it was fixed match and return the bet. Several gamblers said that they were banned for such bets. And casino mustn`t prove anything due to ToS.
You must be playing at untrusted casinos which are not reputed because if the casino is reputed they will never will hold your funds and will always release them and let you withdraw if you win the bet or any gambling game.
For the casino's who are not conserved about the reputations only they will do this tactics of not approving the KYC only to stop people from withdrawing or delay the withdrawal and all these stuff which will annoy the gamblers and they will not come back to such casino sites if they experience these problems.
Nope. It were both cryptocurrency and fiat casinos. The main part of them are well-known, several of them has ANN threads here. Even after KYC they returned me my money and made bet limit about $1-$5. It is standard situation for online casino when some gambler wins too often. Nobody cares about their face when on the other side common unknown gambler.