Recurring tasks that go overdue ...
I have a recurring task in iOS, every 12th and 24th. Sometimes, it goes overdue by a day or two. When I go to complete it (on, say, the 14th or the 26th), the iOS app crashes and the task is not marked complete and not advanced to the next date in the recurrence.
I have no trouble marking it complete on the web or Android versions. It moves properly to its next date.
I also have no trouble marking it complete in the iOS version when it's not overdue.