Ugh, this has to be the second buggiest quest in the whole game (after Blood on the Ice). Every single time I fight Harkon there's something wrong. He's either invisible or invincible, or Serana just won't calm down. But the one that is really affecting me most is that when I do manage to kill him and he begins his teleporting sequence, he seems to die in the wrong place. Instead of being near the altar, he teleports there, then quickly runs to the corner of the room to disintegrate. I'm absolutely at my wits end as to why this is happening, and wondered if anyone knows what's going on here?