To reproduce
 - create a form with a RadPropertyGrid.
 - set ToolbarVisible to true
 - add some properties, but not enough to cause the scrollbar to appear.
 - start and click on the sort button: the sort is changed, but the scroll bar became visible even if it is not needed.
Workaround:
public class MyPropGrid : RadPropertyGrid
{
    protected override PropertyGridElement CreatePropertyGridElement()
    {
        return new MyPropGridElement();
    }

    public override string ThemeClassName
    {
        get { return typeof(RadPropertyGrid).FullName; }
        set { }
    }
}

public class MyPropGridElement : PropertyGridElement
{
    protected override PropertyGridSplitElement CreateSplitElement()
    {
        return new MyPropGridSplitElement();
    }

    protected override Type ThemeEffectiveType
    {
        get { return typeof(PropertyGridElement); }
    }
}

public class MyPropGridSplitElement : PropertyGridSplitElement
{ 
    protected override PropertyGridTableElement CreateTableElement()
    {
        return new MyPropGridTableElemnet();
    }

    protected override Type ThemeEffectiveType
    {
        get { return typeof(PropertyGridSplitElement); }
    }
}

public class MyPropGridTableElemnet : PropertyGridTableElement
{
    protected override void UpdateScrollers(UpdateActions updateAction)
    {
        this.Scroller.UpdateScrollRange();
    }

    protected override Type ThemeEffectiveType
    {
        get { return typeof(PropertyGridTableElement); }
    }
}