check this value for your shadow problems
sc_screen_default.settings.lights.sunPssmSplitWeight = 0.7; //

and these will be the core one to play with
sc_screen_default.settings.lights.sunShadowResolution = 512; //reduce shadow resolution as we are manually setting the shadow range to 5000 and can therefor get away with a small shadowmap
sc_screen_default.settings.lights.sunPssmSplitWeight = 0.7; //high res near splits, low res far splits
sc_screen_default.settings.lights.sunShadowRange = 5000; //manually set the shadow range...we don't need realtime shadows in the far distant! If set to 0 (default) shadow range will be set to camera.clip_far
sc_screen_default.settings.lights.sunShadowBias = 0.001; //set the shadow bias