A friend noticed that he couldn't get "brightnight-smooth" lighting preset to work for him. He wanted to have a night-time version of the map.
I also tried it and couldn't get it to work. I then tried all the other night variants, and they wouldn't work either. The only way I was able to get a night version of the map, is when I used a day-night lighting preset, that would allow the map to switch from day to night tiles.
I started poking around code on git and I noticed this line:
https://github.com/webbukkit/DynmapCore/blob/master/src/main/java/org/dynmap/hdmap/ShadowHDLighting.java#L39
That made me want to try editing the configuration.txt file and change the following line from true to false, as a test:
use-brightness-table: false
That seemed to do the trick, all the night lighting presets worked.
Not understanding exactly what that setting does, I was hesitant to just change it and leave it, thinking that it may affect other maps, without me noticing the change right away. So I then decided to try editing lighting.txt file, and included
use-brightness-table: false
... on all the night view presets. That also worked.
From there I reverted the lighting.txt file, knowing that the file really shouldn't be edited (in case of future update changes)... and I set about adding a night-time preset to the custom-lighting.txt. Again, that also worked.
This leads me to think that maybe you forgot to add that line to the night-view presets in the lighting.txt preset file, and that there is no problems/bugs in the actual code. Since, I'm assuming, configuration.txt should probably leave that value set to true.
FWIW, I didn't test all versions of Dynmap. I've only tried this on the Forge version, so I'm not sure if this problem would show up for other users, using other versions, but I'm guessing it might.