private void gridView_CellLoaded(object sender, CellEventArgs e)
{
    if (e.Cell is GridViewFooterCell)
    {
        var row = e.Cell.ParentRow;
        Dispatcher.BeginInvoke(new Action(() =>
        {
            var aggregatesList = row.ChildrenOfType<AggregateResultsList>(); // the exact type of children that should be used to get the new height may vary based on your column Footer contents
            if (aggregatesList.Count() > 0)
            {
                var height = aggregatesList.Max(x => x.ActualHeight);

                var cellsPanel = e.Cell.ParentOfType<GridViewCellsPanel>();
                PropertyInfo minRowHeightProp = cellsPanel.GetType().GetProperty("MinRowHeight", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic);
                object minRowHeightPair = minRowHeightProp.GetValue(cellsPanel);
                PropertyInfo heightProp = minRowHeightPair.GetType().GetProperty("Second");
                heightProp.SetValue(minRowHeightPair, height);
            }
        }));
    }
}

public MainWindow()
{
	InitializeComponent();
	this.gridView.AddHandler(RadGridView.KeyUpEvent, new KeyEventHandler(OnGridViewKeyUp), true);
}

private void OnGridViewKeyUp(object? sender, System.Windows.Input.KeyEventArgs e)
{
	if (e.Key == Key.Up || e.Key == Key.Down)
	{
		Dispatcher.BeginInvoke(new Action(() =>
		{
			var currentCell = gridView.CurrentCell;
			var row = currentCell.ParentRow;

			// Since the VisualOffset proeprty is protected and you are already inheriting the GridViewRow class, you can just expose it through an extra property in the CustomGridViewRow, instead of using reflection like in this example.
			var visualOffsetPropInfo = typeof(Visual).GetProperty("VisualOffset", System.Reflection.BindingFlags.Instance | System.Reflection.BindingFlags.NonPublic); 			
			var offset = (Vector)visualOffsetPropInfo.GetValue(row);
			if (offset.Y < 0)
			{
				row.BringIntoView();
			}
		}));
	}
}

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

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