I have built many static vehicles such as buildings that are environment mods. A recurring problem I seem to have is when I first make the world, the environment mod is fine. If I go and save the world, and reopen the saved world, the vehicle/building seems to have been gutted. With all of the components such as light, pivots, slides, etc. missing. There are also gaping holes all over. I am not sure what the fix is, but it is currently hindering some of my abilities in the game. I also have these vehicles static, keep activated and invulnerable.