Problem with a style UserControl

Hey Comunity,

I have a problem - how should it be others.

I created a usercontrol, that gets its style by DynamicResource. This control is used for Navigational Purposes. Now I use the control on a UserControl (lets name it A). All wonderfull.

That it looks like when I start the app.

Then I need to add dynamically another UserControl (lets name it B) containing the Navigational Control. Then in A the elements shown above look like that:

Can someone help or explain? Invalidate doesn't work. Dispatcher.Invoke(..Render) doesn't work. Only closing A and reopening A. Then all is good till b overlay A again...