I found the file which seems to be responsible:
wp-content/plugins/all-in-one-event-calendar/app/view/admin/js/pages/event.js
I tried another Minify plugin and added this one to the exclusion list and the calendar plugin worked without any problems. However using BWP Minify and adding it to the exklusion list did not work. I took a look at the cache directory and the event script is still minified.
Any Idea?