I've just replicated the issue in my environment too. However, this seems to be around the source list referenced once the form is published. What is interesting is that it is based purely on the view. If you were to change the Calendar View to that of only the Item or even Current Events, it will work.
I noticed that the only URL type field for the Calendar list type is Banner URL. I'm unable to remove it from the list, but I'm wondering if this is an expected column to have data in it when using the Calendar view.