Okay I think I know ( still try to correct the things in the last post, when I forgot to select the actor in my prject it works only half of the time).
In Stencyl, when there is a collision, there are usually multiple collisions . Why ? Because there's a collision when one pixel point hits another, but there's usually multiple pixel points that hit the collided oject.
So here, the engine will try to kill your actor multiple times, but the second time your actor is already dead. Herein the problem.
So you have to use a boolean
when the actor hits something else.
if hasBeenHit == False:
hasBeenHit = True
kill self
