TabControl: The tab items and their content are not disposed correctly due to the RadTabItemAutoamtionPeer.

Pressing the Home and End keys selects the first/last items even if they are collapsed/hidden.

The scroll buttons are visible when the visible area is enough to display all tabs and the TabStripPlacement is set to Left/Right.

When the window of an application that has a TabControl with Left/Right TabStripPlacement is resized, the measure of the TabStrip is incorrect and the ScrollButtons are in Disabled state. All Tabs should be visible when the window is in its normal state and should be scrollable.

The workaround is to set the IsContentPreserved of the RadTabControl to True.

In version 2016.2.613.45 of the Office2013 Theme, there is a problem in the control template for the RadTabControl. The ContentBorder element properly gets it's BorderThickness from the TemplatedParent, but the PlacementStates VisualStates override it with hard-coded Thickness (0,1,1,1 in the case of the "Left" Visual State) in their storyboards rather than doing an appropriate transform of the Thickness. This makes it impossible to override the BorderThickness for the control in any state other than the default layout without copying and replacing the entire control template. This appears to be a change in behavior since the (Februray 2016?) release, but I cannot be sure as the old theme files were uninstalled during the upgrade and the telerik.windows.controls.navigation.baml file is not properly decompiled in JustDecompile.

Workaround: Set HorizontalScrollBarVisibility property to Visible in order to show the scrollbar: 
<telerik:RadTabControl ScrollViewer.HorizontalScrollBarVisibility="Visible" .../>

or use Loaded event of TabControl and change the Height in order to trigger SizeChanged:
private void xTab_Loaded(object sender, RoutedEventArgs e)
{
    this.Height++;
    this.Height--;
}

The SelectedTabContent is not added when the control is loaded in memory and a we try to create a ImageSource out of the UserControl hosting the TabControl

When you have implicit DataTemplates applied to items the binding expression is lost on selection changed.

Selecting tabs with same names from the drop down menu always selects the first one.

In the VS2010 designer the selected tab is the last one even if the SelectedIndex proeprty of the TabControl is set to 0. The issue can be reprodiced in a scenario where the RadTabControl is defined in a RadWindow control.

Click event of a Button in the HeaderTemplate is not fired properly when another button outside the tab has IsDefault property set to true

SelectedItem does not respect the Reset collection changed action.

When the RadTabControl AllowDragReorder property is set to True and the control contains multiple rows with tabs, the dragging operation cannot be properly executed and completed.

When a TabItem has a width (and the TabControl - don't) and if you try to resize the window so that the width of the window is less than the width of the TabItem - the TabItems start jumping

When a RadDocking is located inside a RadTabControl and the RadPaneGroup contains only one RadPane the content is scrolled(if located inside a ScrollViewer)

Workaround:
Use the PreviewMouseLeftButtonUp and PreviewMouseLeftButtonDown events of the DropDownMenuItem. Handle the first event and invoke DropDownMenuItem.MouseLeftButtonUpEvent in the second in order to workaround the MouseLeftButtonUp event fired from the DropDownMenuButton and to call the logic for selecting the tabitem only when the dropdown menuitem is clicked (not just hovered). 

<Style TargetType="telerikTabControl:DropDownMenuItem">		
        <EventSetter Event="PreviewMouseLeftButtonUp" Handler="DropDownMenuItem_PreviewMouseLeftButtonUp" />
        <EventSetter Event="PreviewMouseLeftButtonDown" Handler="DropDownMenuItem_PreviewMouseLeftButtonDown" />
</Style>

private void DropDownMenuItem_PreviewMouseLeftButtonUp(object sender, MouseButtonEventArgs e)
{		
		e.Handled = true;
}

private void DropDownMenuItem_PreviewMouseLeftButtonDown(object sender, MouseButtonEventArgs e)
{
	var item = (sender as DropDownMenuItem);
	MouseButtonEventArgs mouseEventArgs = new MouseButtonEventArgs(Mouse.PrimaryDevice, 0, MouseButton.Left);
	mouseEventArgs.RoutedEvent = DropDownMenuItem.MouseLeftButtonUpEvent;
	item.RaiseEvent(mouseEventArgs);
}

The CommonStates of the control aren't applied and this is why you can't add any storyboards for the normal and disabled state of the control.

Can't apply transitions when changing the visual state of the RadTabControl or its items