Disappearing units?

[garetjaxusmc 10]

A hello to all; I ran into something interesting with the ambient combat within Arma 2. Now I know that the ACM is supposed to 'clean' up extra units; is there a way to manipulate that in any way? In particular, to keep units around just a little bit longer? Or is this possibly a bug that I just happen to be running into?

I'm asking because I ran into something interesting in a custom mission I made with the generic scenario editor provided: some units would spawn, fight it out with other spawned units, and then just randomly disappear, even after I had fired upon them. (On a side note- ambient combat was selected as 'high'. This was a simple mission with only a handful of initially placed units: a Marine 2-man sniper team, their target of 2 special forces, and the default two sets of 3 or 4 men at their waypoints. I've tried this on multiple maps and have the same results.)

I guess it wouldn't be such an issue if they had disappeared in a forest, but in plain sight it really feels odd to see a fire team and supporting APC headed right for you, firing at you, and then the very next instant, they aren't there.

Thank you for your time.