The ground and stairs textures are glitched and happens to walk through them or the walls or to fell down from the top floor or walk.
- Legacy ID
Just walk through the entrance and try to go upstairs.
Castle in Zub, near Vyshnoye.
I have also experienced this issue. I was able to enter the castle and my body was clipping in the floor. I attempted to go up stair that is inside the building and then I clipped through the stair and was stuck. Within 5 seconds of clipping through the stair I was dead. I received the "You are Dead" black screen.