A few days ago, I started to get a large number of cron errors "Too late for the schedule". Now that I have time to investigate - I see that the task "newsletter_send_all" is never ending/always running. According to AOESchuduler, it started on 2015-09-11 22:30:03, but has never finished.
How can I fix that?
(PS. emails are still being sent by the shop... so thats not an issue).