You can spot them pretty clearly as a bingo card is placed on the screen and the games are rendered against the cards as the slot reels are spinning. Some players have played them enough to be able to spot winning/losing patterns on the cards faster than the reels can render.

Understanding the Game: Unlike traditional slots that work on random number generators (RNGs), bingo slot machines are based on bingo games. Essentially, you're playing against other players, with the outcome of the bingo game determining the slot result.