Too many lights on a surface will sometimes cause it to flicker or blink from lit to unlit depending on your viewing angle.
While making Coldhaven, some of the textures from vanilla Skyrim (like the mountain objects I used from Blackreach) seem to have this issue if even one light source is close enough to light the surface ...
I found this very annoying as a mod author and I tried to place the lights in my mod just far enough away from cave walls or houses so the lighting glitch/flickering wasn't visible.
I do NOT recommend using a lantern or torch when walking around the exterior of Coldhaven because you may experience lighting glitches. The author of RLO says the same thing about his mod; a script is even part of his mod that actively removes the torches from guards so you won't experience flickering in towns.
QUOTE: "The game's engine can't properly handle many additional light sources. When too many light sources are in one area, surfaces produce anomalies like flickering textures and uneven lighting. The more light sources in one area, the more pronounced the light issues." - AKCelsior (https://www.nexusmods.com/skyrimspecialedition/mods/4789)