I found a lot a sedan (same problems for the Offroad) and I have noticed a lot of thing :
1 - When the wheel are not Pristine the Sedan will go in drift mode (impossible to control) that make just no sense, even if there is 3 pristine and 1 damaged. I tried to take out all wheels swap them, nothing when I repair them - perfect.
2 - When we crash into a tree or something and the Hood break we are not able to make the sedan work again, I repaired everything on the sedan but still don't want to start
"The following parts are optional, but recommended for the safety of vehicle occupants:
1x Civilian Sedan Driver Door
1x Civilian Sedan CoDriver Door
1x Civilian Sedan Back Left Door
1x Civilian Sedan Back Right Door
1x Civilian Sedan Hood
1x Civilian Sedan Trunk"
But it looks like they are necessary