Add some logging for the create/destroy, around the add/remove of the listener.
Either the callback is fired twice for an event (unlikely) or there are two listeners.
Actually, when logging in the ClipChanged, could you include the class?
That (hopefully) would print the default toString.
ETA: Also, it's preferable to copy and paste text here, rather than include images.
It's a lot easier for us to work with text.