Hi,
i have the same problem like @marcowaldmeier .
Here some Infos of the Behavour:
on the main events page (month view of current month) mouse over on button for next month (May) and i can see correct url (events/2018-05).
on click on the may link ,overlay with loading spinner appears,
a ajax call (POST) to admin-ajax.php starts with following post-data:
action=tribe_calendar&eventDate=2018-04&featured=false&tribe-bar-date=2018-04
then the url in the addressbar of the browser changes to the correct url (events/2018-05), the same calendar data is loaded with title april 2018 and the filter for date is now suddenly filled (previouse empty) with “04.2018”.
i can send you the systeminfo from post_type=tribe_events&page=tribe-help if needed (but not in public here).