Precalculated Ambient Occlusion has "seams"

When i use the “Generate Ambient Occlusion Mask” (because I want to use it obviously), the calculates AO has Seams between the Models. The seams get more visible with higher quality settings (that I also kinda need).
I tried now many different combinations of Settings, more smoothing, less, more resolution and even less. But the Seam is always there (sometimes more and sometimes less visible).

Screenshot is made with a Material with AO Mask and unlit (so it is not caused by the other real time AO). Also white is where the occlusion takes place (the darker, the less occlusion).