I am getting a weird bug that translates into the game.
I have debugged it to know it is coming from the skylight.
Turning it off removes the bug, but changing settings does not.
That looks like Ambient Occlusion with extreme settings. Have you played with AO parameters in post process? If not, set AO intensity to 0 in your global PP volume and see if they disappear just for the sake of additional debugging.