TreeView: When the header of an Item is set to a TextBox, the selection of a RadTreeViewItem is incorrect

The original reported issue is that the following style does not work as expected.
<Style TargetType="telerik:RadTreeViewItem">
<Style.Triggers>
<Trigger Property="IsKeyboardFocusWithin" Value="True">
<Setter Property="IsSelected" Value="True" />
<Setter Property="Tag" Value="Selected" />
</Trigger>
<Trigger Property="IsKeyboardFocusWithin" Value="False">
<Setter Property="IsSelected" Value="False" />
<Setter Property="Tag" Value="Unselected" />
</Trigger>
</Style.Triggers>
</Style>

This is not supported by the RadTreeView Selection logic. Once the trigger applies with Selected / True, the IsSelected property is Locally set via the selector's code. This means future work of the trigger will not be successful over the IsSelected Property.
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The XAML team has recently reviewed this issue and will not be addressing it as at this time the team is focusing on the bugs impacting the highest number of developers. If you have encountered this issue and it is blocking for your work please contact us through the support ticketing system with details on your setup and a reference to this item.