Angular fullcalendar inital size mobile

Hey,
I have the following problem. When I call the page on which the fullcalendar is embedded, the calendar is collapsed. If I switch once from the mobile view to the desktop view and switch back to the mobile view, everything is correct. Has anyone had this problem before?

Btw I have wrapped the calendar tag into a ngIf and wait for the api call. Thats fixed the problem