oxyplot: plotmodel, scrollviewer in the middle, wpf

I have an oxyplot chart in the scrolviewer and when the scroll is in the middle i cant move chart from left to right/right to left by right button of the mouse. When the scroll is in the top/bottom all is ok. What can be wrong?

<GridGrid.Row="1" ScrollViewer.CanContentScroll="True" Grid.IsSharedSizeScope="True">

<ScrollViewer Name="viewer" VerticalContentAlignment="Bottom" VerticalScrollBarVisibility="Auto" CanContentScroll="False"><ScrollViewer.Content><oxy:PlotView x:Name="plot"SelectiveScrollingGrid.SelectiveScrollingOrientation="Vertical"Margin="3,3" Model="{Binding PlanData}"VerticalContentAlignment="Stretch" HorizontalContentAlignment="Stretch" /></ScrollViewer.Content></ScrollViewer></Grid>