Here’s an interesting article about a guy who broke the scratch-ticket lottery in Toronto.
Essentially the weakness is that the lottery must control how much is pays out, which makes the game not random. In addition, the tickets are designed to entice the scratcher by offering clues and near misses.
Put together, a mathematician working in geology was able to figure out how to use this to break the game. There are even examples of strange streaks for winners. The implication is that some proportion of the winning is engineered outside the legal-appearing veneer on the games, which if true may be the worst thing for state lotteries.