Hair changes to black when changing the view

The hair changes to black literally just by changing the view angle in UE5 (front is normal, side is pure black). What causes this? Hair is exported from Blender (not using any plugins). I use a copy of the MetaHuman hair shader. If I unplug everything from the shader, the behaviour stands. When I plug in a vector3 to the normal input, the behaviour changes (vertical stripes at 0s, more pinkish and brown hues instead of black at 0 0 1, stays the same at 0 1 0), but isn’t fixed no matter what value or hair attributes output I plug in.