AO bake for Kitbash Decals

Im doing some kitbash decals for alphas and normal details. While everything works fine and i baked all my maps, i have trouble getting a AO bake for the method used.

I have my receiver plane on 0.0.0, the highpoly above and the plane duplicated as cage above the high. For the AO pass, i dont get any result, neither with cage or just selected to active. But within the UV Editor, the small thumbnail icon in the image selection shows a greyscale map. So i’m afraid if there is some refresh bug or baking AO to planes need another approach.

Below the order of the setup. 1 Cage Plane, 2 Highpoly Plane, 3 Lowpoly Plane