I don't know of a bug for that exact thing. It depends on what is causing it and if those problems are fixed by other changes for other problems. Like I made a work around for Unity deciding to ignore the ground checks vehicles make to see if they have fallen outside of or under the ground, but that bug caused them to shoot into the air, not down.
That reminds me, I need to respawn vehicles a bit higher, since I've seen the occasional messages where it is having to push them up, since I think their saved position can end up right below ground collider level.
I don't know of any change to that.