The first two pinned rows are scrolled outside of the viewport when you scroll. For example, if you pin 4 rows, the first two will be scrolled and you will see only the second two pinned. This reproduces in the Green, Windows 11, Crystal and Office2019 themes.

To work this around, set the UseLayoutRounding property of RadGridView to "False". Or use a different Telerik theme.

The cell content gets clipped when the width of the previous column changes at runtime. This happens in the Windows11 and Office2019 themes (possibly in others) and only if the clipped cell is position before the right frozen columns area.

To work this around, you can call the Rebind() method of RadGridView, after the column width changes.

In the Office2019 theme, the RadGridView's ScrollBar elements should have transparent background by design. This is the track's background shown behind the thumb element that allows drag-to-scroll. Currently, the ScrollBars have a gray background.

To work this around, you can define an implicit Style in the App.xaml that targets the GridViewScrollViewer control. Then, set its Background property.

<Application.Resources>
    <ResourceDictionary>
        <ResourceDictionary.MergedDictionaries>
            <ResourceDictionary Source="/Telerik.Windows.Themes.Office2019;component/Themes/System.Windows.xaml"/>
            <ResourceDictionary Source="/Telerik.Windows.Themes.Office2019;component/Themes/Telerik.Windows.Controls.xaml"/>
            <ResourceDictionary Source="/Telerik.Windows.Themes.Office2019;component/Themes/Telerik.Windows.Controls.Input.xaml"/>
            <ResourceDictionary Source="/Telerik.Windows.Themes.Office2019;component/Themes/Telerik.Windows.Controls.GridView.xaml"/>
        </ResourceDictionary.MergedDictionaries>
        <Style TargetType="telerik:GridViewScrollViewer" BasedOn="{StaticResource GridViewScrollViewerStyle}">
            <Setter Property="Background" Value="Transparent"/>
        </Style>
    </ResourceDictionary>
</Application.Resources>

InvalidCastException is thrown when the DropIndicatorThickness property of the GridViewHeaderCell is set. Or whenever the DropIndicatorBrush property is accessed. This happens when using the Windows 7 theme. Also, the EnableColumnVirtualization property should be set to False.

System.InvalidCastException: 'Unable to cast object of type 'System.Windows.Media.LinearGradientBrush' to type 'System.Windows.Media.SolidColorBrush'.'

To work this around, you can use an implicit style targeting the GridViewHeaderCell in order to set its DropIndicatorBrush to a SolidColorBrush value.

 <telerik:RadGridView.Resources>
     <Style TargetType="telerik:GridViewHeaderCell">
         <Setter Property="DropIndicatorBrush" Value="White" />
         <Setter Property="DropIndicatorThickness" Value="10" />
     </Style>
 </telerik:RadGridView.Resources>

The column group headers are not displayed when the DisplayIndex property of the GridViewColumn objects is set before the control is loaded.

To work this around, you can set the DisplayIndex of the columns after the RadGridView is loaded.