This is based on game observation. But I saw it happen multiple times. Essentially what happens is the zombie threshold hits five. All zombies in play get Zombie Swarm. A zombie dies and the number of zombies goes down to 4. The zombies retain Swarm. Though I just observed a game where they lost it. When n went under 5. I will keep looking at it and see if I can figure out what is doing it. Or find someone with a zombie bg and see if we can recreate it.
Alternatively could it be based on swarmed zombies providing both the trigger but not being counted when being taken away?
Good thought. Confirmed as the bug. Note that killing an extra real champion does still work, interestingly.
The thing is that animation triggers aren't the same as effect triggers, and while it makes sense that they are in the same location, sometimes the code isn't right or for some reason it wouldn't allow it (for example, in some cases, having the trigger be the same means an extended, long-drawn out set of animations as it iterates over every champion). In ZA/SA's case, it just sounds like the trigger for the animation is on check, rather than on success of check.
