Changing Model3DGroup associated to Model3D with Helix 3D Toolkit

I'm using Helix 3D Toolkit for 3d render inside a WPF application, my ModelVisual3D is binded to "Model".

I setup my model with this:

myGroup =newModel3DGroup();Model= myGroup;

And then i add "n" childerns to that group. My program just refresh those childrens over the time.

Now i want to use visualize an imported .obj file using the helix import, so i did this:

Model3DGroup newGroup =HelixToolkit.Wpf.ModelImporter.Load(myPath +@"\model1.obj");Model=newGeometryModel3D();Model= newGroup ;

but i still see the old group (still refreshed!! i animate that group and even after this it still animates itself!) and i got no errors with my code. In debug mode i can see "model" changing in something that looks right but it doesn't display the new group.

What i'm doing wrong?

I tried to overwrite the old group with the new group but even that has no effect

For give more information here my xaml code who binds "Model"

<h:HelixViewport3DCameraRotationMode="Trackball"><h:HelixViewport3D.Camera><PerspectiveCameraPosition="0,-4,0"LookDirection="0,6,0"UpDirection="0,0,1"NearPlaneDistance="0.01"FarPlaneDistance="1000"FieldOfView="57"/></h:HelixViewport3D.Camera><h:SunLight/><ModelVisual3DContent="{Binding Model}"/></h:HelixViewport3D>