Baked AO map shows unnecessary grey parts along some edges

I imported this cube from Blender with no change of its default geometry and uv wrapping. After baking the maps I found there are some errors in AO map(just like other models I imported to Substance Painter). I tried tweaking the import settings and some bake settings, still couldn't solve it. I'm new to Substance Painter, not sure if this is actually an error. But I think those dark lines are kind of unnecessary which cause extra dirt while using a dirt generator.