Hi Jan,
Thanks a lot for your awesome plugin, I'm trying to set it up with a theme I made for clients. The theme uses a script to check for theme updates. https://kaspars.net/blog/wordpress/automatic-updates-for-plugins-and-themes-hosted-outside-wordpress-extend
Whenever the autoupdater script is included in functions.php, your plugin stops working. The previous/next links on the calendar don't work anymore and return a 500 (Internal Server Error) from the call to admin-ajax.php
Any idea on how to fix this?