I fix the UV layer for the penultimate of your buildings, but for a long time I am surprised at one thing. The simple wall of a building, which could consist of only two triangles, is often more than six. A large number of triangles increases your file. The cityset now has 177kb. My citysets usually range from 90 to 120kb. Smaller files are less burdensome for the game. The ideal wall construction is as I indicated in the picture in red.