Light bleeding into corners in dark dark places or deep areas during daytime

I was building a underground volcano on flat world and then all of a sudden I kept seeing these lighting pixels in corners or edge of blocks when it’s daytime and it’s not because the sun was over me I could see the sun rising lighting underground and I placed more blocks where it kept affecting and didn’t work. And I thought it must be a flat world thing but it wasn’t it was a regular world thing as well.