You should either use ContentControl or ItemsControl as the container for your views. Secondly, if the error occurs in run time, the cause of it could be found in your user code making or handling navigation request for changing view, and also the view initialization code.
Exception thrown by IModuleManager implementations whenever a module fails to be retrieved or fails to retrieve a dependency. In such instance inspect your ModuleCatalog.xaml file or the code bock in charge of retrieving the modules such The CreateModuleCatalog and the ConfigureModuleCatalog methods.
Exception thrown by IModuleInitializer implementations whenever a module fails to load in which the culprit will most likely be located in your module user code. The Best place to start looking will be your module constructor and Initialize methods. Also the duplication libraries in multiple module XAP files as well as libraries found in your Shell Project and one of your module in a Prism application will also raise such exception. Thus, thou shall set the property field “copy to local “on those shared references to false