Been farming Wayrest Sewers I for a healer set to add bubbles to my sanctuary set. Noticed that somehow the walls would vanish, depending on camera angle. Had it one week, but then this week seems it was fixed for me, but others now have the glitch. Either it was fixed, but broke somewhere else for other people or it is just random and never fixed at all. I guess it is something to do with textures, the stuff that paints the wire frames of everything. If you run to the glitch, the wall still stops you, so the wire frame collision detection is still there, it is something with the texture skin that paints the models. As if it turns transparent when it bugs out. A similar thing happens in another dungeon where you can see checkerboard patterns in the distance.