This slot is pure evil. It has potential to reward you with massive wins, but it sucks you really fast with the bonus buys. Also I feel the wheel on 16,20,24 gamble does not give accurate chance of getting to next level ( Already made a thread in this forum for this ).
Back on topic – I also had 0x bonus more than once. What I noticed, also THE BANDIT said that he feels the same way – 12 or 16 spins triggers tend to loose more. I think the reason is that it’s already programed to be a decent bonus and gamble is weighted more to loosing than improving. So I collect any 16 spins that I get from the get go. Doing it this way I had many 200-300x hits (0.2-0.4stake), even had ~1600x.
So my advice would be not to gamble 16 spins ( that you get from trigger ) to the max or do it, but know that you have very small chance to improove
Cheers.