Version 1.5.33 has been released, which fixes the problems mentioned below. I.e. the sync should work fine even if "Upload before download" is turned on and no new duplicates should appear. If you already have duplicates, please just execute "Reset calendars" once as mentioned below to fix the problem.

New features are:

• Tasks in events can be reordered in the edit view.
• Completed 'Tasks in events' can be hidden in the detail view.