Refining the translation of 3D scanned objects on top of the real object

Hi there. I just cant seam to figure, how i can ensure, that my virtual content is always aligned with the real world scenario. after restarts the orientation of the generated room is sometimes different and sometimes not.
With spatial anchors and the prefab spawner i managed to get my items placed but i just cant seam to refine the orientation and scaling of the virtual item to get the positioning in the real world right.