Prism View is incorrectly initialized when associated with a region We have created a SDK sample with a CustomRegionAdapter for the RadTabControl and its implementation can be found in out SDK repository(https://github.com/telerik/xaml-sdk/tree/master/TabControl/PRISM/CustomTabControlRegionAdapter)
You need to implement and register RadTabControl compatible Prism Region Adapter. I did it in our project by search and replace in original TabControl Region Adapter