Corrupted .docx download using phpdocx

I have a project in which we are using phpdocx pro to generate a .docx file in the from templates. I can get the data in to the template easy enough, however when the file is downloaded and opened in MS Word 2010, the program reports that the file cannot be opened because there are problems with the contents, the details being "The file is corrupt and cannot be opened". Word can repair the document, however the issue still stands that it should not be corrupted in the first place.

This is how I'm generating the document:

function generateUnitDesign(){
  if($this->populateRecords()){
      require_once dirname(__FILE__).'/phpdocx/classes/CreateDocx.inc';
      $filename = 'UnitDesignTemplate-'.str_replace(' ', '', $this->rec->title);
      //Create Document
      $document = new CreateDocx();
      $document->addTemplate(dirname(__FILE__).'/templates/unitdesigntemplate.docx');

      // Fill in text fields
      $document->addTemplateVariable('TITLE', $this->rec->title);
      $document->addTemplateVariable('CHALLENGE', $this->rec->challenge, 'html');
      $document->addTemplateVariable('HOOK', $this->rec->hook, 'html');
      $document->addTemplateVariable('RESEARCH', $this->rec->research, 'html');
      $document->addTemplateVariable('AUDIENCE', $this->rec->audience, 'html');
      $document->addTemplateVariable('SUMMARY', $this->rec->project_brief, 'html');
      $document->addTemplateVariable('RESOURCES', $this->rec->resources, 'html');
      $document->addTemplateVariable('REQUIREMENTS', $this->rec->requirements, 'html');
      $document->addTemplateVariable('SCAFFOLDING', $this->rec->scaffolding, 'html');

      $document->createDocx($filename);
      unset($document);
      header("Content-Type: application/vnd.ms-word");
      header("Content-Length: ".filesize($filename.'.docx'));
      header('Content-Disposition: attachment; filename='.$filename.'.docx');
      header('Content-Transfer-Encoding: binary');
      ob_clean();
      flush();
      readfile($filename.'.docx');
      unlink($filename.'.docx');
  }
}

Originally, I was trying to use their createDocxAndDownload() function to get the file, but it would leave a copy of the .docx file on the server, which was not ideal. Am I missing something? Is there someone with more experience with phpdocx to lend a hand?

Edit: Well, I feel like an idiot. After narrowing the issue down to the portion of code that outputs the file, I finally opened the file in a HEX editor and discovered the issue was that after the file was output successfully the web frontend would append the start of it's HTML to the end of the docx file making a 'corrupted' file. This one line immediately after the unlink() fixed the whole thing:

exit;

Pekka: If you would like to answer this with the new information, I'll accept your answer.

Solution

After narrowing the issue down to the portion of code that outputs the file, I finally opened the file in a HEX editor and discovered the issue was that after the file was output successfully the web front end would append the start of it's HTML to the end of the docx file making a 'corrupted' file. This one line immediately after the unlink() fixed the whole thing:

exit;