Warning <None> Object has overlapping UVs.

i have two times this error and also Info <None> Lightmap UV are overlapping by 26.1%. Please adjust content - Enable Error Coloring to visualize.

So i deleted nearly everthing only the building stands (built in Unreal Engine)…Problem still here.

I am new, so maybe a silly question: how can i look which item does that problem? <None> i cant click…