Sometimes in specific places lighting is aggressively glitched, will not update. Torches do not work, broken blocks leave airspaces with block light level 0, and even sunlight stops updating, acting as if the torches do not exist or the blocks are still placed, even if there is a clear sight to the sky. Possibly lag related, computer can only handle small render distance. Occurrs in newly generated chunks, sometimes fixed with relogging but not always. Fixes itself with time.