[Crash when joining Harkon]

When I try to join Harkon after he offers to turn me into a vampire my game will crash when teleported to the Volkihar Cathedral.

 

Here is an example of it happening.

https://giant.gfycat.com/UnconsciousRareGordonsetter.webm

I guess Modwatch is down right now so I can't upload my load order.

 

Things I have tried:

1) I have cured myself of lycanthropy.

2) I contracted vampirism and waited 3 days to complete the transformation.

3) I added the vampire lord spell to make sure that wasn't a problem and it worked fine.

4) I dismissed all followers (besides Serana) before going to Harkon.

 

I really don't know what else to try. I loaded Dawnguard.esm in TES5edit to check for compatibility problems, but I don't really know what to look for.

 

[BOSS or LOOT]

So I have heard about a new program called LOOT and it is supposed to be like BOSS. Is it any better or what?