Occasionally, one player will not be able to move a vehicle at all, despite not being apparently hindered by any obstruction. The car will appear to vibrate very quickly on the affected player's client. If another player hops into the driver seat and moves the vehicle as little as a foot, the first player will then be able to drive the vehicle as normal.
Cars are also sometimes appearing to be stuck, but then catching up with whatever movement commands were issued by the player during this time period. I teleported forward about 30 meters, phasing through a rock wall and several trees, only to find my front two tires ruined.
Also related, I hurt my leg and damaged my pants and boots by leaving the passenger seat of a vehicle that was stuck in this state.