Random calendar appearing bottom left of the page when creating new events

I've discovered what I believe to be a small bug in the plugin combined with a trigger in our custom development, which is a small calendar hidden in the bottom left corner of the screen, that is some times turned on and opens in that bottom left corner.

The first image of the calendar folded away into a small line is something that you will see even on a fresh install of the plugin.

Our custom development is technically hiding the date fields that it might be used on and auto-filling them in, which I guess is triggering the calendar to open, but since the fields are hidden, it has nowhere to go, so just opens where it is.

Obviously I understand you probably can't advise on our custom part, but is it correct for the closed calendar to be there in the first place?