Blood of Arlathan Bug

So, I've been having this bug for months now and I finally reached the point where I'm just pissed off. 

I have started that quest numerous times in hope it might fix itself but nothing happened.

It's the scene where you need to defend the area while (for me) Bellars tried to open the gate from the other side. 

Usually I am supposed to fight the Venatori but none of them spawn for me. I have had that issue before and was a le to solve it with just walking around and waiting (which still, was very annoying)  but after 30 Minutes of waiting nothing is happening. No one is spawning and Bellara is still trying to open the gate,