/usr/bin/mixxx:11:MixxxMainWindow::finalize:MixxxMainWindow::confirmExit:MixxxMainWindow::closeEvent:QWidget::event:QApplicationPrivate::notify_helper

The Ubuntu Error Tracker has been receiving reports about a problem regarding mixxx. This problem was most recently seen with package version 2.0.0~dfsg-9, the problem page at https://errors.ubuntu.com/problem/cd21d447dfa2b30214ef605ac2c0cfcff4468031 contains more details, including versions of packages affected, stacktrace or traceback, and individual crash reports.
If you do not have access to the Ubuntu Error Tracker and are a software developer, you can request it at http://forms.canonical.com/reports/.