If you're spectating a player playing a beatmap with SuddenDeath mod, from the Spectator's PoV, you won't immediately get a fail even if the player missed a note and failed. It's either going to just wait until the HP drained down to 0 or showing "fake-passed" result screen if the song is close enough to completion before HP gets to 0. The player's cursor simply stucks when the player missed the note.
This is probably because of the delay in streaming the Replay data from the player.
This is probably because of the delay in streaming the Replay data from the player.