You automatically fail because, if you don't, people would start doing verdure/inferno until boss pops, force DC and then come back and redo. IMO its not a bug, its a countermeansure because all players are cheaters unless they prove the opposite. I don't like it either, but i agree with it since, even with it failing people STILL fail in this leves on purpose to keep them...just imagige if you could just skip the failing part.