Harkon won't transform into a vampire first time... he just keeps going " arrgggg " and nothing.. i've tryed -

Reloading from earlier save before i started the dawnguard still no help... is there a fix around for this?.. don't wanna waste my 300+ hours... already lost my last 2 characters with hundreds of hours invested.. this is really bothering me.. can anyone help?

this is also stopping me from doing the Dragonborn DLC... because this quest line will be broken and that ruins my whole RPG experience lol