Tween, unexpected end

Hi,
I’m trying to simulate ocean waves for a presentation. In order to make it look random I’ve added 2 waves with a coded tween each. Once a tween is over it gets recalculated and moves to the other edge. And so and so.
The problem here is sometimes this tweens comes interrupted with no reason and neither a TweenEvent is dispatched. So… why does my tween end unexpectedly or how can I detect it in order to make it run again?

Thanks a lot