On my system i can easily reproduce the effect in game master mode. Simply adjust the game time of day until the problem appears. The exact times affected change if different weather is selected, but the effect occurs for at least part of each night, and on both Arland and Everon.
Obviously my laptop is barely capable of running this game, so i have almost all the the visual settings at their lowest value. I haven't tried every possible combination of visual settings, but for each parameter i have tried all their settings while leaving the others unchanged. No visual setting affects whether the effect is occuring, nor does the lighter night setting in game master mode, only the time of day and weather. I've joined a few multiplayer games, but had to abandon them when night fell.