If you are winning fairly and by the book, a casino should under no circumstance steal your winnings from you or frustrate you out of it, but many of them do it. It is advisable to choose reputable/popular casinos, that is not to say you cannot run into some problems when you use them, but it can be easily resolved and the casino would not want to tarnish their reputation, so if it is discovered that you won fairly, they would settle it ASAP.