Manipulation Points not showing on LineAnnotation

I add a LineAnnotation programmaticly to my surface and want to readjust it just like in the Examples Suite via clicking and draging the ends of the annotation.
As long as i dont use a Theme everything works fine. But when applying a custom theme the Manipulation points are not there anymore (and not only visualy, clicking at the end of the line also does not work. Furthermore the mousecursor does not change to a cross when hovering above the annotation end).

This is my Custom theme code:

<ResourceDictionary  x:Class="Reprocess.SciChartDisplay.CustomTheme"
    xmlns="http://schemas.microsoft.com/winfx/2006/xaml/presentation"
    xmlns:x="http://schemas.microsoft.com/winfx/2006/xaml"
    >       

<!--  *************************  -->
<!--  Colors and Brushes  -->
<!--  *************************  -->

<!--  Chart Brushes  -->
<SolidColorBrush x:Key="TickTextBrush" Color="Black"/>
<SolidColorBrush x:Key="MajorGridLineBrush" Color="LightGray"/>
<SolidColorBrush x:Key="MinorGridLineBrush" Color="LightGray"/>
<SolidColorBrush x:Key="SciChartBackground" Color="White"/>
<SolidColorBrush x:Key="GridBorderBrush" Color="#102A47"/>
<SolidColorBrush x:Key="GridBackgroundBrush" Color="Transparent"/>
<SolidColorBrush x:Key="RolloverLineBrush" Color="#33FD9F25"/>
<SolidColorBrush x:Key="CursorLineBrush" Color="#996495ED"/>
<SolidColorBrush x:Key="RubberBandFillBrush" Color="#33333399"/>
<SolidColorBrush x:Key="RubberBandStrokeBrush" Color="#77999999"/>
<SolidColorBrush x:Key="LegendBackgroundBrush" Color="AliceBlue"/>

<SolidColorBrush x:Key="LabelBackgroundBrush" Color="#AA6495ED"/>
<SolidColorBrush x:Key="LabelBorderBrush" Color="#FF6495ED"/>
<SolidColorBrush x:Key="LabelForegroundBrush" Color="Black"/>

<SolidColorBrush x:Key="TextAnnotationForeground" Color="#EEEEEE"/>
<SolidColorBrush x:Key="TextAnnotationBackground" Color="#AA6495ED"/>

<Color x:Key="AxisBandsFill">White</Color>

<!--  Default Series Colors  -->
<Color x:Key="UpWickColor">Gray</Color>
<Color x:Key="DownWickColor">Gray</Color>
<SolidColorBrush x:Key="UpBodyBrush" Color="Gray"/>
<SolidColorBrush x:Key="DownBodyBrush" Color="Gray"/>

<Color x:Key="UpBandSeriesLineColor">#22117711</Color>
<Color x:Key="DownBandSeriesLineColor">#22111111</Color>
<Color x:Key="UpBandSeriesFillColor">Black</Color>
<Color x:Key="DownBandSeriesFillColor">Red</Color>

<LinearGradientBrush x:Key="MountainAreaBrush" StartPoint="0,0" EndPoint="0,1">
    <GradientStop Color="Gray" Offset="0"/>
    <GradientStop Color="#000710" Offset="1"/>
</LinearGradientBrush>

<Color x:Key="MountainLineColor">Black</Color>
<Color x:Key="LineSeriesColor">Black</Color>
<Color x:Key="ColumnLineColor">#11FFFFFF</Color>
<SolidColorBrush x:Key="ColumnFillBrush" Color="#11FFFFFF"></SolidColorBrush>

<Brush x:Key="OverviewFillBrush">White</Brush>


<Brush x:Key="ScrollbarViewportBackgroundBrush">White</Brush>

<LinearGradientBrush x:Key="DefaultColorMapBrush">
    <GradientStop Offset="0" Color="White"/>
    <GradientStop Offset="0.5" Color="White"/>
    <GradientStop Offset="1" Color="White"/>
</LinearGradientBrush>

Any suggestions?