VisualStateManager ignores RepeatBehavior="Forever" - wpf

Question

I have a very simple VisualStateGroup that should start gradually (cubic ease) spinning animation in the Spinning state and stop it as soon as it exits the state. However the animation stops after the first round as if RepeatBehavior="Forever" was completely ignored by VisualStateManager:
<VisualStateManager.VisualStateGroups>
<VisualStateGroup Name="SpinningStates">
<VisualState Name="Spinning">
<Storyboard>
<DoubleAnimation Storyboard.TargetProperty="(UIElement.RenderTransform).(RotateTransform.Angle)"
Storyboard.TargetName="SpinnerIcon"
To="360" Duration="0:0:1" RepeatBehavior="Forever" />
</Storyboard>
</VisualState>
<VisualState Name="NotSpinning"/>
<VisualStateGroup.Transitions>
<VisualTransition To="Spinning" GeneratedDuration="0:0:1.0">
<VisualTransition.GeneratedEasingFunction>
<CubicEase/>
</VisualTransition.GeneratedEasingFunction>
</VisualTransition>
</VisualStateGroup.Transitions>
</VisualStateGroup>
</VisualStateManager.VisualStateGroups>
Is not RepeatBehavior="Forever" supported by VSM transitions? Is there a way to fix the problem?
Infrastructure code for example above:
<UserControl x:Class="Controls.Spinner"
xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation">
<VisualStateManager.VisualStateGroups/> <!--from above-->
<TextBlock x:Name="SpinnerIcon" Text="X" RenderTransformOrigin="0.5,0.5">
<TextBlock.RenderTransform>
<RotateTransform x:Name="preventFreeze" />
</TextBlock.RenderTransform>
</TextBlock>
<UserControl/>
code behind:
public static readonly DependencyProperty SpinProperty =
DependencyProperty.Register("Spin", typeof(bool), typeof(Spinner), new PropertyMetadata(true, OnSpinChanged));
private static void OnSpinChanged(DependencyObject d, DependencyPropertyChangedEventArgs e)
{
if (d is Spinner spinner && e.NewValue is bool shouldSping)
{
VisualStateManager.GoToElementState(spinner, shouldSping ? "Spinning" : "NotSpinning", true);
}
}
punlic bool Spin
{
get { return (bool)GetValue(SpinProperty); }
set { SetValue(SpinProperty, value); }
}