First off.. Anything scaled in sketchup is going to export skewed and off.. So, always save as new and explode everything before exporting to dwg/dxf. If that doesn't work. Open it up in Revit and export it from there. Works everytime

one way to do it is to explode everything before export. also, Revit works at great work around. You just insert your sketchup model(which you should explode because anything scaled comes out inaccurate) into revit and export out as dwg/dxf