I've had this problem since I started playing the game sometime in January.
It's some sort of graphical glitch. There are tones of flickering black rectangles but only in character hair. I've tried to debug the problem to no avail. I've tried using 3 different graphics drivers (Adrenalin 19.10.1, 20.2.2, and 20.4.2). I've tried tweaking all the graphics settings and setting them all to low. I tried playing in windowed, windowed fullscreen, and fullscreen mode. I tried starting a new game. Nothing worked. This issue isn't present in any other game either, just The Outer Worlds, which indic