Patchy Shadows

Sorry for the probably noob question but can someone please show me what I’m doing wrong here. I try to build the shadows for a bunch of basic cubes at the start of a project but they turn out patchy. This happens on all build quality settings.
I have a lightmass importance volume and a sphere refection capture in the scene.

Also, I cant take in engine screenshots now. It says it cant make the directory to save them in, even though the folder is already there with other levels’ screenshots in it.