How to use default WPF animations with Mahapps

Question

Im using Mahapps for animating ListBox items everytime an item is added or sorted.

    <DoubleAnimation Storyboard.TargetProperty="Opacity" From="0" To="1" Duration="0:0:1" />
<DoubleAnimationUsingKeyFrames Storyboard.TargetProperty="(FrameworkElement.Height)" DecelerationRatio="0.8">
     <EasingDoubleKeyFrame KeyTime="0" Value="0"/>
     <EasingDoubleKeyFrame KeyTime="0:0:.5" Value="25"/>
</DoubleAnimationUsingKeyFrames>

The animation starts on the top of the control with Height=0 and then expands it to bottom and also expands all items located behind of this. The problem is when using Mahapps the animation starts on the middle of the control and then expands to top and bottom. I would like to use the default animation setup with Mahapps library.

I tryied to use the DoubleAnimation from the default System library but it seems I have the same problem.

Thank you very much.