Click Event not working anymore when using Helixtoolkit.SortingVisual3D

I want to add transparency to Objects (without loosing the Click-Event). Google told me to try SortingVisual3D. Without SortingVisual3D everything (except transparency) worked well, Click-Events also.Now i tried to implement it (simplified code):

Public SV3d As New HelixToolkit.Wpf.SortingVisual3DPublic 
Model3DUI As New ModelUIElement3D

'Apply geometry
    Model3DUI.Model = geometry 'skipped geometry code in this post
'Add Click Event
    AddHandler Model3DUI.MouseLeftButtonUp, AddressOf ClickEvent
'Add to SortingVisual3D
    SV3d.Children.Add(Model3DUI)
'Add to ViewPort
    Viewport.Children.Add(SV3d)
'Setup SortingVisual3D
    SV3d.SortingFrequency = 2
    SV3d.Method = HelixToolkit.Wpf.SortingMethod.BoundingBoxCorners
    SV3d.IsSorting = True

Basically it works fine, everything renders as it should and transparency is working too. But for some reason now the Click Event doesn't work. Anybody has an idea what i'm doing wrong?

I'm not very experienced with Helixtoolkit, so it could be that my way is completely wrong.