Yes, this lighting problem is a bug that only occurs in the "Sunset" mood and when using a mod.
It is possible that while eliminating
this problem, in the mood Sunset too many lights were switched off. It is also possible that the problem existed before.
In Sunset mood, this removes the illumination of half of the blocks on the map, including the grid on the side of the road, the glass on the office blocks, and the spots in the indoor stadium.
In addition, the headlights of a custom vehicle are not turned on.
BTW: The checkpoint lamps are also not switched on. Please note that the lamps of the offroad checkpoint (1-2-8) are always on. Also in Sunrise and Day and without using a Mod. This is another independent bug...