In front of the Hungering Destroyer there is some sewer pipes. If you go in one of them in the middle right at the end, you get stuck in a loading screen. After a very long while (abnormally long), you get remove from the Castle Nathria from the back entrance in the sewer mouth.
I can give a more precise locations with a video if devs needs it.
3 people in the raid try to repro it with me when I found that out, they all had the same problem