I've gotten to the point where I've become a vampire in the quest-line and I've been instructed to talk to garen marathi.

After which i talk to him and he tells me about the bloodstone chalice (no " you're not a vampire bug) he then tell me to follow him to the bloodstone chalice. He then proceeds to walk away from the chalice and onto the second floor of the castle near the balcony, where he stands there indefinitely he does not move and "enabling" and "disabling" him seems to do nothing. I've gotten past this before by forcing the quest with "setstage" but the bugs just get worse. Harkon will not get out of his seat to speak his speech, the vampires and crashed wagon will not appear during the moth quest, the dungeon entrance to find the moth priest will NOT even show up in the world, and when i teleport into the dungeon it's totally empty.

I've played dawn-guard before on release without bugs and this problem, I've tried a new save, re-installing the entire game, re-downloading the content, running vanilla and cleaning the save, all of which are resulting in the same things happening exactly. I've disabled and wiped all my mods and it still occurs; it's game breaking and totally ruins the vampire path.

I was hoping somebody had a similar problem with a fix that could shed light onto this infuriating bug.

Many thanks.