Whilst playing on a world (tested in normal & superflat), after a few map restarts, the lighting inside any building will gradually get worse every restart and act either as if the inside of a building is exposed to the sky (with no roof) or has random bright or dark patches throughout.

I have tested a building in a few scenarios on a test map. Having the building start from the ground up, have the building raise into the clouds, or have the building floating in mid air, all have the same effect:

Note that each compartment is unlit, I have added no light source of any kind.

Restarting the map or the game does not resolve the issue.

Placing any light sources in any of the bright spots does not fix this, or does placing a light source in the dark spots (however it will light up these areas, but the exact same lighting pattern persists even if a light source is placed or destroyed).

Additionally in certain scenarios, placing a light source in any of the affected areas causes a strange dark border affect as shown below:

Whereas, it should usually look like:

On the main map I am working on, a building I have just above the set sea level, the inside of the building is far too bright. The below image shows an enclosed room with no light sources placed.

The first image is during the day (showing a block light level of 2, however looks fully bright):

And this is during the night:

As stated, restarting the map or the game does not fix the issue, and remains as shown. Placing or removing light sources also does not fix this.

This issue started during snapshot version 18w50a and still appears in the latest snapshot 19w04a.

Please note however that this issue does not affect any buildings that are completely submerged underwater. I have not seen any instance of the above issue for any building fully underwater. However this issue will affect buildings partially submerged (built below the sea and extends into the sky).