I am not sure I understood your scenario correctly.
The SelectionChanged event is a routed event and it is possible that you are handling the events of the inner TabControl from code that is meant to handle only the events of the outer TabControl.
To work around this, set the e.Handled = true
; when you perform an action as a result of an event.
This way the event will not be routed to any handlers in the visual tree that were not meant for it.
Please correct me if I am missing something here.
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