When resetting the dropdown filter of the calendar to show all events, some events are missing (for example holidays) due to the webservice function not retrieving all entries.
A full page reload is required.

The affected file is calendar/externallib.php.

An easy solution might be to trigger the page reload when resetting the filter to show all events.
Otherwise the function has to be extended to allow of loading all events. 

I'm not sure if it is to be defined as bug but for the user it is percieved as bug.