I encountered a bug when using copy: true. If you drop something, it will be created twice.
I think this is because the model is changed and the gu-transit element is inserted as well. That's why we then have two occurences of the same object, while only one of them is linked to the model

demo:
http://46bb3f4c.ngrok.io/

If you point me in the right direction, that would be great and I will submit a PR. Thanks ahead.