Sub-assemble position in two primary compents

Two Four Drawer Cabinets.skp (1.8 MB)
The attached model contains five components.- (Cabinet Assembled - 33 Base - 4 Drawer), (Cabinet Assembled - 27 in - 4 Drawers), (Drawer - 4 3/8 Deep - Left Side Plate), (Slide - Drawer Left Rail), (Slide Rail - Left Hand Assy), (#6 x 1/2 Fllat Hd - #2 Phillips Slot), (#6 Threaded Insert - Birch). When the screw is inserted into the 33 Base - Left Side Plate, it is not in exactly the same position as when it is inserted into the 27 Base - Left Side Plate. As near as I can tell the components are identical - and I would expect the position to be identical. I suspect the axis between components may not be exactly parallel and perpendicular. Is there a method for determining the axis are exactly parallel and perpendicular? Any other suggestions?