I worked in a casino and ate lunch on occasion with the Head of Surveillance. He told me a story of a couple of guys who absolutely had a system for beating some of the slot machines. He had absolutely no clue how they did it.

The two guys were neighbors in Florida, but would act like they didn't know each other in the casino. Sit near each other, not acknowledge each other, that sort of thing. But they would play and win at statistically impossible rates. Switch machines at seemingly random. The machines they would play on would be pulled and checked but they were in perfect working condition.

The security team looked into the two men, and they apparently owned some kind of company that provided gaming supplies to casinos, but nothing to do with slot machines. Real weird stuff.