I recently noticed a pretty big bug- all shadows in Minecraft were missing, every block had the highest light level. It's like a constant Nightvision effect, but without the effect bar, blue tint, bubbles, etc. I think it started when I closed the game with the Nightvision effect. After that, the shadows on ALL worlds/servers were gone- new ones, already existing ones, even on Hypixel. However, mobs were still spawning. To fix it myself, I had to set the brightness to moody and turn Mipmap off. Everything works like usual for me now, even after changing the light settings. I think I could repeat the process to eliminate the shadows again, though. Please fix this bug, I heard it already exists for years and it kind of feels like cheating. 

(the attached pics are older, I already fixed the issue for myself and repeating it doesn't work right now!)