There is a fundamental problem with the shopping cart. When sets with a Windows Internet Explorer product in the shopping cart, then liked change shipping or payment method, nothing happens, you can click anything, its blocked.
It works with the Web browsers on Apple devices. However, there is the problem with the Ä, Ö, Ü, etc. In the german Translation-File "de-DE.plg_system_vmuikit_onepage.ini" i must use Codes for that Types like: "Ändern" for "Ändern etc. Now displayed me the words correct in the Buttons, but if you change a Shipping or Delivery Methode, after that the words writes with the Code.
Please test it on my Web page, they can comprehend it, but look that you have a Browser with German Settings.