Was in an elite Titan run, everyone was waiting at the rainbow door, and the red puzzle was about halfway done when one of the 3 red people disconnected, then left the group.
The other 2 were locked in but unable to continue, and unable to go back to the beginning. It was obvious that he waited until they had crossed the point of no return, then logged out and logged back in on another character.
If you're like me, and don't like to waste your limited DDO time because of one person's deliberate sabatoge, I'll PM you the individual's name.