Unkillable black crow in maps

I'm currently playing a bleed build and there is a crazy bug that just won't let me beat this boss probably because it goes way past the damage threshold that it can normally take.

So the Crow boss just like campaign has 3 stages. First where you encounter him, then after doing some damage it goes to the second area and this is where i have the issue. I believe because the bleeding is aggravated he quickly takes alot of damage and goes past the damage threshold that is needed to go to the third stage which is the pit area.

No matter what I do it won't stop attacking and when I continue to attack, it stays immune at around 5% hp and won't go to his last area.

I took a whole video of the incident since screen shots won't really show anything.

https://www.youtube.com/watch?v=9s88sB-5094

This is a video of a different person but SAME EXACT situation.