Ashar, The Sand Mother --- Bugging behind reward door

I was finally finishing my 3rd Ascendent quest and on the final momments of the fight the boss started to dive and surface in different places of the arena which the last one was behind the door.

As a ranger I have no skill that hits through the wall, unlike some other classes.

Right now just lost all the time making up to there and as well as the best chance I had so far to kill the boss.

[url]https://imgur.com/a/stbGK0q[/url]