I was just doing a run in tier two and started lagging. This happens occasionally and seems to go away after a loading screen, so I kept playing normally for a while before reaching the gate to the next level down. However, when I reached the gate, the other players saw me as standing a fair distance to the south. I had been standing on what I thought was the gate for a few minutes before we realized what was going on. There were no error messages of any kind, which seems like a pretty big problem.