The Path property of the breadcrumb cannot be set because the FullPath that comes from the selected treeview item doesn't match a valid path from the breadcrumb. Currently, when the text mode is disabled the breadcrumb control is constructing its Path by using the ItemsSource's objects ToString() method. For example, if the control is populated with objects of type MyDataItem the path will be something like this - "MyApplicationNamespace.MyDataItem\\MyApplicationNamespace.MyDataItem
". On the other hand the tree view will use its Text property to construct the FullPath of the treeview items. For example a tree item's path could look like this - "Item1\\Item1.1
", which won't be a valid path in the breadcrumb.
In order to achieve your requirement you can enable the TextMode of RadBreadcrumb and set the TextModePath property to the same property name as the value of the TextSearch.TextPath attached property set on the treeview. This way the paths in both controls will use the same pattern and values which will bring the desired effect of synchronization between the components.
For your convenience I attached a sample project demonstrating this implementation. Please give it a try and let me know if it works for you.