I didn’t know it previously, but it imported the meshes. So, I put it together, grouped the meshes, and then did a few light bakes after changing the scene to static lighting. The result is similar to yours, where there’s inaccurate darker areas and lighter areas on different parts of the fence. And that’s without the material applied, or any material. Now I’m trying to get a better lighting of it by changing various settings. I’ll also try to generate lightmaps with different settings to see if it works.
Thanks for your help, my game has too much of this problem. I wish it was an easy method. 
I tried a bunch of things. I increased directional light intensity, enabled DFAO, generated lightmaps several different ways, increased cubemap resolution for the skylight and modified other skylight settings, increased shadow bias (accuracy) and slope bias (accuracy on vertical surfaces), increased shadow resolution (also in the directional light), and when I finally tried to merge meshes of the fence (the two posts, and two other pieces) the engine crashed. I had also changed World Lightmass settings, from reducing the number of indirect / skylight bounces (from 5/5 to 3/2, respectively) to changing Quality and Smoothness back to defaults (from 2 Quality / 0.9 Smoothness to 1 / 1). What’s interesting is the lighting for the fence changed, but it merely changed where the artifacts occurred and how much…mostly making it worse.
One thing I caught was micro-gaps in the fence’s fill mesh, where each fence slat is supposed to be aligned next to each other. The mesh is not complete in that regard. Open the fence mesh, and probably other meshes, in a 3D modeling application such as Blender or Cinema4D / 3dsMax, and check them for gaps / overlaps / double vertices, edges, faces / other problems. Those kinds of things could result in incorrect lighting.
Thank you for trying so much and helping.