i'm pretty sure that's a beamng issue, i remembering it happening in other maps too like wcusa and italy
I cant do anything about it, maybe someone will kindly update the bus missions someday, because they are unrealistic/outdated and buggy.
Very good map as i remember, but after this update i only get 10-15fps but about a 6-9months ago i dont remember after which update i just cant play it
I get even lower, but I've noticed that if I look away from the car - the fps is totally fine! And in my case it started lagging after 0.30 update. I tried deleting some objects from the map until I've realised it's the vehicle that's causing fps drops, and when I tried different cars - some of them fix the issue and some of them drop it insanely, but keep in mind that on other maps all cars perform identically.