The designer of VS crashes with a "Key cannot be null" when custom markup extension is used in Style Setter. This reproduces in the sample app attached in the blog (http://www.telerik.com/blogs/bring-office-2016-inspired-style-to-your-app-with-ui-for-wpf) on the TextBlock of the RabRadioButton HeadingStyle (snapshot attached) if you open MainWindow in Designer. Runtime everything works as expected.

The KeyTips are not displayed correctly when the RadRibbonView is Minimized and you show the keytips for the first time.

Available in LIB version: 2014.3.1319

The KeyboardNavigation throws null reference exception when you try to move through the DropDownButton of the QAT and we does not have the button in the style targeting the QAT.


Available in LIB version: 2016.3.1121

Available in LIB version: 2015.1.2303

Workaround for this bug is setting Style.Triggers for this scenario.

<Style BasedOn="{StaticResource RadRibbonSplitButtonStyle}" TargetType="telerik:RadRibbonSplitButton">
  <Style.Triggers>
    <MultiTrigger>
      <MultiTrigger.Conditions>
        <Condition Property="IsChecked" Value="True"/>
        <Condition Property="IsEnabled" Value="True"/>
        <Condition Property="CurrentSize" Value="Medium"/>
      </MultiTrigger.Conditions>
      <MultiTrigger.Setters>
        <Setter Property="Foreground" Value="{DynamicResource CheckedBrush}"/>
      </MultiTrigger.Setters>
    </MultiTrigger>
  </Style.Triggers>
</Style>

Available in LIB version: 2016.3.1003

The selected tab content ScrollBar appears when there are RibbonGroups which size can be changed to smaller size.

Available in LIB version: 2014.3.1409

RotateTransform is not applied correctly on elements defined in the Content of the window.

Reason for declining: The issue appears to be in the framework as it is not calculating correctly the transformation and instead of rendering the transformation it apply a Clipping to the parent element. You could solve the issue by two different approaches: you could either set the UseLayoutRounding of the Window to false, or set the Width/Height properties of you element to be Integer numbers, not double (10.782). You can reproduce the same behavior with the MS Window simply set its UseLayoutRounding to true. You can find attached project reproducing the issue only with MS controls.

Workaround:
In the Loaded event of the RibbonWindow, use the Telerik.Windows.Controls.RibbonView.Shell.WindowChrome class to get the current window and set its ResizeBorderThickness property to 0. 

public MainWindow()
{
    InitializeComponent();
    this.Loaded += MainWindow_Loaded;
}
 
void MainWindow_Loaded(object sender, RoutedEventArgs e)
{
    Telerik.Windows.Controls.RibbonView.Shell.WindowChrome chome = Telerik.Windows.Controls.RibbonView.Shell.WindowChrome.GetWindowChrome(this);
    chome.ResizeBorderThickness = new Thickness(0);
}