XD It has been a long time since I have seen this happen.
What you are meant to do is walk though this door and load the next section….that not what happened to me. For some reason my characters continued walking upwards until they went though the edge of the screen.
O_O I was just stuck staring at this cave, unable to do anything.
There is no hope.
Additional: just got an update for the game; I can now go though the door.