Now that I've reread your requirements, my plugin won't help. chrisinfinger has the correct solution as you must take into account what items are alive at the time of the next spawn. Having said that, your pathfinding is wrong. 1) I'd put the behaviour on the family, not the individual sprites, 2) you call "Find path" and that's it. You need to add "On path found" and then call "Move along path". Remove the "is not moving along path, as that will be true as it's trying to calculate the path.