I've encountered this bug a lot in the past...
Only the first person that enters a vehicle is able to use the smokewall of this vehicle.
So e.g. if my m8 is entering the vehicle as the gunner and afterwards I enter for commander I don't have any smokes.
When we change and I enter first for commander and he joins me later for my gunner it's fine .. I got all smokes etc.
I also lose the smokes if I get out of the vehicle to repair it and get in later I lost my smokes again.
Kinda annoying but I don't if this is a basic ArmA problem or if you can fix it.