- MahApps.Metro version 1.6.4
- OS: Win10 1803
- Visual Studio 2017 15.7.4
- .NET Framework 4.7.2
The DataContext of the (Transitioning)ContentControl is bound to a class with a Enum property CardTypeValue which fires INotifyPropertyChanged. The ContentTemplate is set via DataTriggers (one for each Enum value). The default ContentControl recognizes the notification and changes its ContentTemplate. The TransitioningContentControl doesn't do this.
ContentControl :

TransitioningContentControl:
