I tested this on my side but the text was displayed properly. My guess here will be that the used font doesn't work well with WPF or there is an issue with the encoding. Can you try to reproduce this also with a native TextBlock or TextBox control? I also attached my test project.
Regards,
Martin Ivanov
Progress Telerik
Want to extend the target reach of your WPF applications, leveraging iOS, Android, and UWP? Try UI for Xamarin, a suite of polished and feature-rich components for the Xamarin framework, which allow you to write beautiful native mobile apps using a single shared C# codebase.