Light level bug at irregularly continuous chunks

Error chunk that has problem with light level appeared in survival mode.

Within dark region, light level of sky represents 0 without no ceiling block.

The region is up to y=95 high.

At some edge of it, light level is gradated up to 14, and zombies doesn't get burned in the region.

Placing block will updates light level partially, but it's gradating like block's light level

However, placing at y=80 or above will correct light level on 3x3 chunk.

Reproducibility is confirmed with the same seed(7501060747914640433), but at different locations.

Before I see them, I entered and exited the Nether.

 

Sorry for bad English, but I hope this information will help developers.