Select not working after POST action="#"

Select not working after POST action="#"

The following example should reproduce the problem.

The switch works after loading the page

After hitting the send button, the switch does not show any element anymore.

Tested on Chrome, Android and IOS

I guess I do fall for some super easy error here. Please help me. I'm running it on a FLASK server.
  1. <html>
  2. <head>
  3. <meta http-equiv="Content-Type" content="text/html; charset=utf-8">
  4. <meta name="viewport" content="width=device-width, initial-scale=1">

  6. <title>title</title>
  7. <link rel="stylesheet" href="https://code.jquery.com/mobile/1.4.5/jquery.mobile-1.4.5.min.css">
  8.     <script src="https://code.jquery.com/jquery-1.11.3.min.js"></script>
  9. <script src="https://code.jquery.com/mobile/1.4.5/jquery.mobile-1.4.5.min.js"></script>
  10. </head>

  12. <body>
  13. <div data-role="page">
  14.   <div data-role="main" class="ui-content">
  15.    <select name="ss" id="ss" data-native-menu="false" data-icon="grid" data-iconpos="left">
  16.      <option>1</option>
  17. <option>2</option>
  18. <option>3</option>
  19. <option>4</option>
  20. </select>
  21. <form action="#" method="post">
  22. <button type="submit">send</button>
  23. </form>
  24.   </div>
  25. </div>  
  26. </body>
  27. </html>