I have had this happen multiple times with Phase Retreat both outdoors an in Lion’s Arch during an instants. One thing it also can do is get you stuck in combat which means the only way to get out of it is to log out. When you log back in you are still under the world, but now your out of combat so you can use a way point to resolve it. If it happens in an instance the only way to resolve it is to swim to outside the boundarys so it kicks you from the instance.