There is a game engine limitation using mods that add a lot of art assets. In this case UC & CL together will cause graphical artifact/renderer log errors. Other mods that can contribute to this issue include the Warfare Expanded and City Styles mods. Other than using only one of these asset heavy mods at a time, you can also disable certain NFP DLC packs. I believe the one that had the best results when disabled was the Gaul/Byz pack.