I’m still trying to solve this one. It looks like it’s related to Volumetric Lightmaps. Because the weird shadows go away when I disable it on Show->Lighting Features. And they change place depending on my Volumetric Lightmap Detail Cell Size value. And it’s not related to memory because when visualizing the Volume Lightmaps I have sample spheres even inside the black shadowy areas. And those are not black. They’re shaded normally, as the other spheres on non-black areas.
I’m using UE 4.20.2