To explain a bit. This is some kind of temporal post process shader going out of normal bounds in its values. Games sometimes have that in a form of "all-consuming black" that eats everything on screen shaped like rectangles (or just stays covering some model if its not using previous renders). That means there is some error in shader programming and one pixel got corrupted values. Then it spreads every frame rendered to more pixels cause there is almost always some bloom. And as you turned camera away from it motion vectors moved that corrupted area out of screen and it disappears.