Error using Windows Phone 8.1 mmppf - getting parse exception when trying to navigate to page

Question

I'm getting a really weird exception when trying to navigate to a page in a Windows Phone 8.1 application (universal)

A first chance exception of type 'Windows.UI.Xaml.Markup.XamlParseException' occurred in MyApplcation.exe
WinRT information: Cannot create instance of type '%0' [Line: 25 Position: 44]

It also says:

The text associated with this error code could not be found.

I have some code in my MainPage.xaml.cs that navigates to a page called details:

 private void Button_Click(object sender, RoutedEventArgs e)
        {
            Frame.Navigate(typeof(Details));
        }

Details has very little code:

<Page
    x:Class="MyApplcation.Views.Details"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    xmlns:local="using:MyApplcationViews"
    xmlns:d="http://schemas.microsoft.com/expression/blend/2008"
    xmlns:mc="http://schemas.openxmlformats.org/markup-compatibility/2006"
    xmlns:mmppf="using:Microsoft.PlayerFramework"
    mc:Ignorable="d"
    Background="{ThemeResource ApplicationPageBackgroundThemeBrush}">
    <Page.Resources>

    </Page.Resources>
    <Grid>
        <Rectangle Fill="#FF152853" HorizontalAlignment="Left" Height="260" VerticalAlignment="Top" Width="491" Name="videoBack"/>

        <Image x:Name="preview_image" HorizontalAlignment="Left" Height="260" Margin="0,10,0,0" VerticalAlignment="Top" Width="56" Stretch="UniformToFill"/>
        <Border x:Name="layoverBorder" CornerRadius="50" BorderBrush="Transparent" BorderThickness="2" Margin="196,63,196,689" Background="#FFFEFEFE" Opacity="1"  >
            <Image x:Name="layoverImage" HorizontalAlignment="Left" Height="51.671" Margin="20,14.674,0,0" VerticalAlignment="Top" Width="56.372" Source="ms-appx:///Assets/triangle-64 (2).png" Stretch="None" RenderTransformOrigin="0.5,0.5" UseLayoutRounding="False" d:LayoutRounding="Auto">
                <Image.RenderTransform>
                    <CompositeTransform Rotation="90.899"/>
                </Image.RenderTransform>
            </Image>
        </Border>
        <mmppf:MediaPlayer x:Name="player" Source="{Binding Video}" Margin="0,0,0,587"/>
    </Grid>
</Page>

When I remove the <mmppf:MediaPlayer... line the page navigation works correctly.

I have no clue where to start since the exception thrown is so vague.