A simple way to test it:
create superflat world,the commands: /tp ~ 255 ~ and /fill ~-10 ~ ~-10 ~10 ~ ~10 stone
Related issues
Comments
migrated
MC-109120
Parts of area under blocks set with /fill are still fully lit clientside
Resolved
Duplicate
0
migrated
Barteks2x
(Unassigned)
Unconfirmed
Minecraft 1.10.2
Retrieved
Just a simple lighting glitch that happens all the time. Mojang did release a snapshot once upgrading lighting, but I guess it was too much to be fully released.
To fix it on Windows, press F3 + A to reload all chunks, or F3 + T to reload resource pack. If neither works, reload your world.