i have the same issue every event we have had the fps drops extremely low, like colds mission it was fine until we used the stranded crew and it spawned in extra AI (mods shouldnt impact fps...) just try it load your 40 mods and set a firefight between 50 AI and try it without mods. To conclude my point mission makers should watch out how much AI they have in the field at a time. PS mso only had the problem after 2-3 hours of gameplay and without the headless client