There are a few places in some episodes where it is possible to get completely stuck as a result of falling or being smacked into something by an enemy. For example, it is possible in The Saboteur, just after you make the stairs appear and do the fight before entering the doors to the final defend sequence, to fall between the platforms and get stuck in a specific spot, rather than fall right through to your death or the area below where you went to unlock the stairs. You cannot jump out, wiggle out, etc. You are hopelessly stuck, unless maybe you have a hero with a movement ability like Mellka. This happened to me as Galilea and after spending five minutes trying to wriggle free, I just quit and rejoined.
I propose that it be possible, maybe limited once per mission per player, to teleport back to the current respawn area after a 10 second channel at no cost to your lives (to prevent people griefing, though it is not like they cannot intentionally die, anyway). This avoids the other solution that wastes far more time, which is to quit the mission then rejoin, which tends to take close to two minutes in total. Also, with a 10 second channel, I cannot see it being used to cheat your way out of bad spots since you would presumably be interrupted if under attack.