I know there are currently known issues with cars and persistence. I will let you decide if this issue overlaps with those, or is a separate problem.
If you find a car spawn, and then make modifications to the car (add/repair wheels, replace other parts, put items in the inventory). Then run far away from the car - I will guess it's related to the network bubble so maybe >1km?. Then return to the car, you will find it has reset back to the state you found it in when it spawned.
I'm assuming this effects all cars, but I have personally seen it happen to the sedan and the offroad.