Worked in 4.5.3. Does not work from 4.5.4.
Using calendar's page fragment for repeatedly opening and closing the popup is not working correctly.
When you open popup, close the popup and then you try to open it again, the popup will show up, but is immediately closed. It is hard to reproduce manually, but it is easily reproduced in tests.
Calendar issues resolved in 4.5.4 link
The fragment is clicking to the input for invoking the popup, but is clicking on the popup button (the button next to the input) for closing the popup. Could there be some unhandled events?