Hi Florent,
Thank you for attaching your project to help us find the problem. I have traced down a bug in the SDK which deletes the interactor for a FrameworkElement when the element is unloaded and loaded again. We have a solution for it and it will be included in the next release of the SDK.
The only workaround I have found is what you have already mentioned, to recreate the UserControl object each time you want to show it.
Best regards,
Eddie