Heatmap with contours show 2 tooltips

Hello,

I am working on a heatmap chart with contours. The dataSeries are binded to DataSeriesInViewModel in the viewmodel, where DataSeriesInViewModel is defined as:

DataSeriesInViewModel = new UniformHeatmapDataSeries<int, int, double>(zValues2d, 0, 1, 0, 1)

where zValues2d contains the grid values data.

In addition there is binding to ZMax, ZMin which are the max, min values of zValues2d and also ZStep which is the number of steps for the contours.

The problem is that one can see two tootips and that those are not showing the same value.

<s:SciChartSurface x:Name="sciChart" Grid.Column="0" ChartTitle="{Binding ChartTitle}">

    <s:SciChartSurface.RenderableSeries>

        <s:FastUniformContourRenderableSeries x:Name="ContourSeries"
                                              AntiAliasing="True" ZMax="{Binding ZMax}"
                                              ZMin="{Binding ZMin}" ZStep="{Binding ZStep}"
                                              DataSeries="{Binding DataSeriesInViewModel}">
            <s:FastUniformContourRenderableSeries.ColorMap>
                <s:HeatmapColorPalette  Maximum="{Binding ZMax}" Minimum="{Binding ZMin}">
                    <s:HeatmapColorPalette.GradientStops>
                        <GradientStop Offset="0.0" Color="{StaticResource ColorMapColor_1}"/>
                        <GradientStop Offset="0.2" Color="{StaticResource ColorMapColor_2}"/>
                        <GradientStop Offset="0.4" Color="{StaticResource ColorMapColor_3}"/>
                        <GradientStop Offset="0.6" Color="{StaticResource ColorMapColor_4}"/>
                        <GradientStop Offset="0.8" Color="{StaticResource ColorMapColor_5}"/>
                        <GradientStop Offset="1.0" Color="{StaticResource ColorMapColor_6}"/>
                    </s:HeatmapColorPalette.GradientStops>
                </s:HeatmapColorPalette>
            </s:FastUniformContourRenderableSeries.ColorMap>
        </s:FastUniformContourRenderableSeries>

            <s:FastUniformHeatmapRenderableSeries  x:Name="HeatmapSeries"
                                                   Opacity="0.8"
                                                   UseLinearTextureFiltering="True"
                                                   AntiAliasing="True"
                                                   DataSeries="{Binding DataSeriesInViewModel}">
            <s:FastUniformHeatmapRenderableSeries.ColorMap>
                <s:HeatmapColorPalette  Maximum="{Binding ZMax}" Minimum="{Binding ZMin}">
                    <s:HeatmapColorPalette.GradientStops>
                        <GradientStop Offset="0.0" Color="{StaticResource ColorMapColor_1}"/>
                        <GradientStop Offset="0.2" Color="{StaticResource ColorMapColor_2}"/>
                        <GradientStop Offset="0.4" Color="{StaticResource ColorMapColor_3}"/>
                        <GradientStop Offset="0.6" Color="{StaticResource ColorMapColor_4}"/>
                        <GradientStop Offset="0.8" Color="{StaticResource ColorMapColor_5}"/>
                        <GradientStop Offset="1.0" Color="{StaticResource ColorMapColor_6}"/>
                    </s:HeatmapColorPalette.GradientStops>
                </s:HeatmapColorPalette>
            </s:FastUniformHeatmapRenderableSeries.ColorMap>

        </s:FastUniformHeatmapRenderableSeries>
    </s:SciChartSurface.RenderableSeries>

    <s:SciChartSurface.XAxis>
        <s:NumericAxis DrawMajorBands="True" AutoRange="Always" LabelProvider="{Binding XAxisLabelProvider}"/>
    </s:SciChartSurface.XAxis>

    <s:SciChartSurface.YAxis>
        <s:NumericAxis DrawMajorBands="True" AutoRange="Always" LabelProvider="{Binding YAxisLabelProvider}"/>
    </s:SciChartSurface.YAxis>

    <s:SciChartSurface.ChartModifier>
        <s:ModifierGroup>
            <s:RolloverModifier ShowTooltipOn="Always" UseInterpolation="True" ReceiveHandledEvents="True"/>               
        </s:ModifierGroup>
    </s:SciChartSurface.ChartModifier>
</s:SciChartSurface>

<s:HeatmapColorMap Grid.Column="1" Margin="2"
                   HorizontalAlignment="Right"
                   VerticalAlignment="Stretch"
                   Background="{StaticResource ThemedSurfaceChartBackground}" 
                   Foreground="{Binding Source={x:Reference Name=sciChart}, Path=Foreground}"
                   ColorMap="{Binding Source={x:Reference Name=HeatmapSeries}, Path=ColorMap.GradientStops, Converter={StaticResource ColorsToLinearGradientBrushConverter}}"
                   Minimum="{Binding ZMin}" 
                   Maximum="{Binding ZMax}" 
                   TextFormatting="0.00" Opacity="0.8" BorderBrush="#777" BorderThickness="1" Orientation="Vertical"/>

I also tried to assign to the contour chart the colormap from the heatmap using:

 <s:FastUniformContourRenderableSeries x:Name="ContourSeries"
                                   AntiAliasing="True" ZMax="{Binding ZMax}"
                                   ZMin="{Binding ZMin}" ZStep="{Binding ZStep}"
                                   DataSeries="{Binding DataSeriesInViewModel}"
                                   ColorMap="{Binding Source={x:Reference Name=HeatmapSeries}, 
 Path=ColorMap.GradientStops,
 Converter={StaticResource ColorsToLinearGradientBrushConverter}}">

but then I still see two tooltips but no contours anymore.
In fact i would like to know what I do wrong here, and how to see only one tooltip.

thanks a lot for your help,

Thomas