I found what the issue was - Over time I populated several towns with around 60 "rifleman light" 2 or 3 various helis and several opfor ground vehicles plus around 40 items of ammo "empty"etc EACH! - all this added up to around at least 900 items and resulted in the AI malfunctioning!

I setup another single town arrangement as above and AI is behaving again except for one minor thing - opfor heli's are shooting at incoming player in heli / quadbike etc but when player is on foot they spin slowly and eminate smoke as if shot when they weren't!

Regards
Greg