@jackpot_jane That's the near-miss effect in action. Slot designers program those 'almosts' deliberately - your brain interprets them as 'almost winning' rather than 'completely losing'.
PokerStars Casino is the worst for this. Their slots seem to have more near-misses than anywhere else. Stick to their poker rooms instead - at least there you're playing against people, not algorithms designed to mess with your head.