Too many TreeViewItems are created internally when using virtualization. This causes the tree to consume large amount of space when performing virtualization intensive tasks like CollapseAll or ExpandAll.

The XAML team recently reviewed this issue and will not be addressing it.
On ExpandALL / CollapseALL virtualization creates / recycles / reuses containers - RadTreeViewItems. You cannot be sure when the GarbageCollector will free up the currently unused containers.
Also after even number of invocations (ExpandAll + CollapseAll), the containers that are not freed up from memory is not increasing - it is constant which means there is no memory leak to worry for.

When two equal objects are used in the source collection, the first is always selected when you try to select the others.

Workaround when TreeView is not databound.

Instead of adding objects directly in the TreeView's Items Collection, add RadTreeViewItems.
For Example, instead of
 treeView.Items.Add(1), 
treeView.Items.Add(2)

do

 treeView.Items.Add(new RadTreeViewItem(){Header = 1}, 
 treeView.Items.Add(new RadTreeViewItem(){Header = 2}

Workaround when TreeView is databound.

For example , if we databind the treeview to collection of DataItems and some dataitem is located in multiple places in the source collection.
Solution => Wrap the DataItem class in new class - DataItemWrapper. It can hold the underlying DataItem, add additional property  (for exampel ID) and override the Equals and GetHashCode methods.
This way different DataItemWrapper objects can hold equal DataItem objects. In such way if you bind the treeview to collection of DataItemWrappers the selection will be successful.

DECLINED:
The XAML team recently reviewed this bug  and won't be adressing it in future. It can be actually considered as feature request because selection should have notion for selected containers.
Unfortunately, the initial code design of the RadTreeView does not have such notion and the complexity of adding such feature now is very big.

Now if you add a content to the panelbar the content inside will receive tab navigation only once due to the items control nature of the control.

The XAML team has recently reviewed the status of this issue and won't be addressing it in future releases.
In order to make the content (items) of a specific RadPanelBarItem (X)  focusable with tabKey, set TabNavigation="Local" on X.

DropDownButton is leaking.

When TreeView is placed inside floating VS ToolWindow and item is selected the visual state remains unchanged after focus leaves the TreeView.

When you place a DataTrigger whithin a CellTemplate, it is being ignored by RadGridView for WPF

Workaround ( until fixed ) - set the ContentTemplate of the cell via Style in a static resource instead.

Add a DragMode that doesn't swap the items but inserts the DraggedItem on the drop position.

The XAML team has recently reviewed this request and will not be addressing it as at this time the team is focusing on the requests impacting the highest number of developers. If 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.

Loaded event of the RadTabItem's content is fired twice in WPF.

Declined: The behaviour is caused due to the way how the WPF framework operates with ContentControl and their Content property(the RadTabItem is HeaderedContentControl which derives from ContentControl). The Content property is automatically registered to the LogicalTree when it is set, this is causing the first loaded event to be fired. After a selection is made the RadTabControl inserts/visualizes the Content of its selected RadTabItem in its ContentPresenter, this causes the control to fire its loaded event as it is loaded into the VisualTree.

private void Content_Loaded(object sender, RoutedEventArgs e)
{
	if (VisualTreeHelper.GetParent(sender as DependencyObject) != null)
	{
		// Execute the logic for LoadedEvent.
	}
}

A selection in RadListBox, RadColorPaletteVIew, RadTreeView. RadGridView etc. cannot be made with touch gestures when the control is inside a ScrollViewer.


Reason for declination:
This is not a bug in the touch logic of the controls. The selection does not work because the manipulations of the ScrollViewer are enabled and the scroller captures the touch and marks the touch events as handled, leaving the ScrollViewer the only element to receive touch events. There are at least two possible solutions for this.

1.If you have access to the ScrollViewer, you can set attached TouchManager.ScrollViewerSwipeMode for the ScrollViewer to Self.

<ScrollViewer telerik:TouchManager.ScrollViewerSwipeMode="Self" />

2. If you do not have access to the ScrollViewer, you can use a combination of two attached properties, for the elements inside the scroller. The two properties are two of the attached TouchManager properties - TouchMode and ScrollViewerSwipeMode.

<ScrollViewer>

   ...

      <telerik:RadCartesianChart telerik:TouchManager.TouchMode="Locked" telerik:TouchManager.ScrollViewerSwipeMode="Parent" />

Instances of the Buttons in ToolBar are not removed correctly.

EDIT: We are marking this item Declined.
We are unable to detect any memory leaks with WPF or SL toolbar with Q2 2015 dlls.

Please open a new support with details if you encounter any memory leak issues with RadToolbar.

When using binding to check state and dynamically adding subitem to a praticular items, the parent items check state is incorrectly set to Off (from ON) although the child item state is also On.

Marking this Declined. Binding to CheckState is not supported in MVVM scenarios. Please use the approach described here =>
http://www.telerik.com/help/wpf/radtreeview-howto-tri-state-mvvm.html

When value types are inserted in the Items collection of RadTreeView and root values are duplicated in the children a StackOverflowException is raised after a call to ExpandAll.

The XAML has recently reviewed the status of this issue and won't be addressing it in future releases.
This is a design limitation - RadTreeView does not support duplication of value types in its Items / ItemsSource collections. 
This potentially can cause troubles with virtualization / selection / expandALL features.

Binding to IsChecked property doesn't work in TwoWay mode (ConvertBack doesn't work).

Declined.
IsChecked / CheckState are supported only in xaml-defined RadTreeViews. In databinding scenarios use the approach described here =>
http://www.telerik.com/help/wpf/radtreeview-howto-tri-state-mvvm.html

When the RadTreeView is virtualizaed, the images are  not shown. This works when the tree is bound to collection of objects and the DefaultImageSource is bound.

Reason for deletion:
The workaround is easy - just bind the DefaultImageSrc, ExpandedImageSrc to string properties from the ViewModel.
Also, a possible fix would slow down the virtualization process in the RadTreeView.

We have a RadTreeView with "Visibility" property set to "Hidden".
We add dynamically RadTreeViewItems to the RadTreeView.
If we change the "Visibility" to "Visible" - the RadTreeView is NOT displayed.

Originally this item is logged for scenario with XBAP. Currently we are unable to reproduce such issue with WPF 4.0 and latest version of our controls.
Please open a new support thread if you encounter similar issues at your side.

Customers request that the chart show one additional point on the left and one additional on the right. This way RadChart creates a nicer illusion of a zoomed in graph.

REASON FOR DECLINATION
This is supported out-of-the-box by the new RadChartView.

ToolBar: ToolBarTray doesn't respect ToolBar's HorizontalAlignment property.

ToolBarTray is actually a Grid supporting Band and BandIndex properties of the RadToolBar.
To simply position RadToolBars with Horizontal/VerticalAlignment properties you can use Grid instead of RadToolBarTray.

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.