A default cube exported from Blender shows this issue(several vertical lines are dark) of baked AO in Substance Painter. I encountered this issue from texturing a model with a layer of dirt where I surprising found some lines have much more dirt than others. After some tests I found out it was the AO problem. Eventually I tried to use this default cube from Blender to see if there would be any issue. Again there was but I really don't know why. I never change export settings in Blender and here are my Substance painter project and bake settings
I think I find out the reason. If I click the button on the right of "High Definition Meshes" and select the exact same mesh from local disk then bake again AO and it solved. It's weird that I tried using "Use Low poly Mesh As High Poly Mesh" which I thought it would work from its literal meaning however it didn't. But If I only have one mesh do I have to select itself as high poly mesh every time just for baking AO? It's confusing.