Collapse the stack completely to an editable poly and do a “Reset xForm” in Max. If the location of the mesh is different from its pivot point, then Unreal will read the pivot point and transform the location of the mesh relative to that pivot point. E.g., if I have a scene where a chair is located at -100,0,0 and my pivot point is 0,0,0; then the chair upon import to Unreal (assuming I do not simply import the mesh into the content browser but rather directly into the scene itself) will appear at coordinate -100,0,0 instead of 0,0,0. If I want the chair at 0,0,0 then the mesh must be located there and the pivot point located there. Reset xForm erases the transformation history of the mesh so that Unreal doesn’t try to read that whole history in the FBX (and therefore screw it up).