When returning to the overworld after spending an extendes period of time in the Nether, there is a lighting issue where spots that are merely covered by single blocks become void of all light whatsoever, such as under a tree, or a tiny 1-2 block outcropping on a mountain despite light sources being present in the dark areas. Dark areas occasionally have impossibly hard edges. Frequently happens after returning from the nether, is fixed by placing or breaking a block within the dark area