Thank you for the provided code snippet.
I was able to reproduce this behavior on my side. Therefore, I have logged it in our Feedback Portal where you can track its progress. What I can suggest as a workaround is to set the theme to the whole application. You can do that with StyleManager by setting the StyleManager.ApplicationTheme static property before the InitializeComponent(); method.
StyleManager.ApplicationTheme = new Office2016TouchTheme();
I hope this approach is applicable to you. In addition, I have updated your Telerik Points for bringing this behavior to our attention.
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