There's a http://i43.tinypic.com/fz5dme.jpg. If I don't pay attention and make sure I activate the door I'll go right through to the "nothing" world.
I had this problem happen last time I played but the gap wasn't as wide. I have been in the cave once to get the crew to plunder and the door was ok then. But this time I came back to get my share of the loot, when I left there was this problem.
I just installed the Unofficial patch yesterday and also the patch for DLCs so I think those would have fixed any problem like this. Has anyone else seen this issue with their Dunbarrow cave door?