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OoperDuper, about the error on export, I haven't seen that particular sequence before. Generally, something along these lines concerns an odd bit of geometry somewhere in the mesh you are trying to export. If I was smart enough to keep previous versions, I try the latest to see if will export correctly, Then the next version back, etc. I have found that I've left some errant vertex or poly around that the exporter doesn't know what to do with. If I don't have the older versions, I make a duplicate mesh, move it to a separate collection, and cut the mesh in half, try to export each half. If one half does export and the other doesn't, then I split the one that doesn't in half again, repeat until I find the section giving the problem and rebuild it. Not sure that will fix it, but the only thing I know.
As for the road shader issues, that goes back to the beginning of the scripts. They were mostly written before S397 and Blender switched to PBR based rendering. So there are no real PBR shader assignments in the scripts are at this time. The Legacy Diffuse Shader (the default assignment) only supports one UV map. You might try the Legacy Special Shader. It has 4 UV maps. They are named as pre-PBR maps, but they should show up in mat editor as ABCD UV maps, in the same order. Haven't tried that yet.