Lighting doesn't update properly

[Letus252]

Video link https://www.youtube.com/watch?v=5Ue7ULgai-o

Short description of the problem:
Lighting doesn't update properly and seems to behave as if I didn't place any block. No, I'm not using fullbright nor any texturepack. I'm playing on 1.8.9 forge, the patcher is the only mod installed, and I turned off all patcher settings. (Youtube link instead of pasting the video directly into github because it's too big (~30MB).

Why this is a problem:
I wanted to play on my survival world "fairly", without any mods except cosmetic and performance-related ones. This bug can often cause lighting to behave as if I had fullbright on (especially when mining).