Material Ambient Occlusion input problem

Hey everyone. I don’t know if it’s a bug or it is how it supposed to work in UE 4.2, but I’m getting very weird results when I plug my AO map into dedicated Ambient Occlusion input for the material. I get very nasty artifacts all over my mesh and in general the shading of the mesh doesn’t look right and it’s driving me crazy.
Here’s the screens:
AOinput.jpg MAT_AOInput.jpg

However when I plug my AO map directly into BaseColor input the result looks way better and more correct
BaseColorInput.jpg MAT_baseColor.jpg

I also tried my AO map in Toolbag 2 and it looks just fine so it’s not the problem with my AO bake

Does anyone know what is happening? Why the dedicated Ambient Occlusion input behaves like that? Am I doing something wrong?

P.S. Sorry if I posted this in the wrong place. I just though it relates to rendering