If you're crossing between sims on a vehicle (typically in a high-prim AV) and get an "Expired region hand-off" message and fail to cross into the new region all sorts of weird and horrible things seem to happen but typically you and your vehicle end up in different sims. For you/me this seems to mean that your controls are grabbed by something that is no longer in the sims and nothing seems to be able to extricate you except logging off. While this is happening you vehicle is now out of control in the other sim and you can't retrieve it because you can't do anything but log off. This can mean a vehicle can travel onwards into other sims unless something obstructs it. This can get even messier if you have additional passengers and/or your crossing near a sim corner where 3 or 4 sims join. Can this problem be fixed by if any person on a vehicle fails to cross a sim border the whole vehicle and any other passengers are kept in the same sim?