WPF，关于控件可视状态，麻烦看下这段代码


<Grid>
        <Rectangle Name="Rectangle1" MouseEnter="ColorChangeMouseEvent" Margin="198,17,0,0" Height="88" 
VerticalAlignment="Top" HorizontalAlignment="Left" Width="100">
            <VisualStateManager.VisualStateGroups>
                <VisualStateGroup Name="MouseStates">
                    <VisualState Name="BlueState" />
                    <VisualStateGroup.Transitions>
                        <VisualTransition To="BlueState" GeneratedDuration="0:0:5">
                            <VisualTransition.Storyboard>
                                <Storyboard>
                                    <ColorAnimation To="Blue" Storyboard.TargetName="rectBrush" Storyboard.TargetProperty="Color"/>
                                </Storyboard>
                            </VisualTransition.Storyboard>
                        </VisualTransition>
                    </VisualStateGroup.Transitions>
                </VisualStateGroup>
            </VisualStateManager.VisualStateGroups>
            <Rectangle.Fill>
                <SolidColorBrush x:Name="rectBrush" Color="Orange"/>
            </Rectangle.Fill>
        </Rectangle>
    </Grid>private void ColorChangeMouseEvent(object sender, MouseEventArgs e)
{
    if (Rectangle1.IsMouseOver)
    {
        VisualStateManager.GoToElementState(Rectangle1, "BlueState", true);
    }
}
当把鼠标移到矩形上时，颜色渐变，5秒钟后，恢复成Orange颜色，因为BlueState状态的颜色和初始的颜色是一样的。不过：
请你调试3次（每次都重新调试），3次当中，你一定会遇到有一次，颜色一直都不恢复成Orange颜色，
这是为什么呢？请问