help with applescript running export script please

I have an applescript that I'm using to open a DPF in AI2017 and then running the ExportAsDWG script (copied from the Scripting/Sample Scripts folder). File opens and then Applescript bounces a message

Script Error

Adobe Illustrator got an error: Illegal argument - argument 2

- Required value is missing

Result

error "Adobe Illustrator got an error: Illegal argument - argument 2

- Required value is missing" number 1243

Is the related to the export as options possibly?

Any help appreciated!

Here is the modified ExportAsDWG script

var docRef = app.documents.add();

var groupItems = docRef.groupItems;

var groupRef = groupItems.add();

var pathItems = groupRef.pathItems;

// Save document as AutoCAD DWG file.

var destFolder = Folder.selectDialog('Select the folder to export the AutoCAD(DWG/DXF) file to:');

if (destFolder) {

  exportAutoCADOptions.exportFileFormat = AutoCADExportFileFormat.DXF;

  exportAutoCADOptions.exportOption = AutoCADExportOption.MaximumEditability;

  exportAutoCADOptions.version = AutoCADCompatibility.AutoCADRelease18;

  docRef.exportFile(destFile, ExportType.AUTOCAD, exportAutoCADOptions);

}

Here is the applescript

tell application "Adobe Illustrator"

  activate

  set inputs to "Macintosh HD:Users:bbb:Desktop:TEST:Test_PDF.pdf" as string

  set outputFolder to "Macintosh HD:Users:bbb:Desktop:TEST:Final.dwg" as string

  set params to {}

  open file inputs

  do script "CGExportAsDWG"

  close current document

end tell