You need to change how you construct the environment, due to how the lighting system works, each mesh gets processed individually and some of the settings that improve rendering speed will cause a slight difference in lighting for each mesh. To avoid this, try to make a surface like those out of a single mesh rather than multiple meshes. You can actually just scale a wall section to the proper size but even making a unique mesh that’s the size you want is a better method. Using multiple meshes is not as good for performance since it increases the number of draw calls and the visible polygon count and since those meshes are so simple it doesn’t save that much in terms of memory using instancing.
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