Blocky shadows on landscapes

It seems no matter what kind of settings I use in lightmass world settings, I get this blocky self-shadowing on landscapes. The landscape resolution does not seem to matter, I resampled it all the way to 4081x4081 but no luck. Static lighting resolution inside the landscape details, I tried at 2.0, but still no difference. Anyone have any ideas?

did you find a way to fix this? I have this problem now