Thanks for bringing this bit up @dennis. At this point, this is expected behavior.
The reason you see the Element does not exist on this page notification is because copy/pasting elements actually creates a different node ID completely. So the original node only exists on it’s original page.
This is where the Replace element with class name comes in. The action list doesn’t show the elements being affected because the animation is no longer applied to the same element — instead it is applied to the class name associated with that element.
We are discussing this further internally to identify how we can improve this piece of IX2. I’ll keep you all posted if we start making more changes.