The video seems to be missing a few frames at the end, so I'm guessing that what happens is that remove element fails, with no error message displayed to the user.
There are various errors in the platform that are not displayed to the user and are 'hidden'in the log. We should and do plan to improve our error notification capabilities, so that the modeler is not left in the dark, resigned to searching in the log. See feature #387.
If I've misunderstood the nature of the problem, please let me know ...
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