When i try and use the /fill command to cover up lights, a light level of at least 1, sometimes up to 7 i've seen it always appears on top of said block covering them up and the only way to get rid of it is to place a block over the light coming through, it started happening not to long ago and it has caused many problems in building so i have to make it block by block now
the other screenshot is a light that won't work correctly that is still causing issues
I even tried in another world to see if its replicable and it did the same thing
It even shows the light on mobs like theres light sources above the block