Upon loading onto a stage from the Arcade, I was the second person in the party. Within seconds, the party leader departed.

The first part of the stage appeared cleared and I advanced towards the party button to the remainder of the stage. The door "behind" the button was already closed [image has mildly edited and resized]: http://imageshack.us/photo/my-images/845/imstuck.png/

Well, that was a waste of 10CE...