It's there since EA, you have a doorway or passage and click on the floor behind it, but you're actually clicking on the passageway area at some height, so it looks like you"re on the floor behind it but you're not. And then the door closes, or instead of going through the passageway, you just turn back to where you were.
Very annoying, but now I stumbled upon a variant that is more than annoying. I wanted to cast cloudkill in a passage behind an open door, and the skull icon was visible on the floor where I wanted it. But the door bug intervened and the cloudkill materialized on the doorway and thereby, on my own party. It kind of sucked.
Please can you fix this in patch 7 ?