I had the same problem. After baking stationary direct light my exponential heght fog coloured up and filled my whole scene. You can fix that in fog details with setting Static Lighting Scattering Intencity by 0.
I had the same problem. After baking stationary direct light my exponential heght fog coloured up and filled my whole scene. You can fix that in fog details with setting Static Lighting Scattering Intencity by 0.