When I move a task on google mail for Android from one calendar to another, the task list on the Thunderbird desktop shows me two copies of the task! see image2 When I try to delete the original task in thunderbird desktop from the task list I get the prompt: see image1 When I change the calendar on the desktop, the same prompt occurs. I can delete the moved copy of the task from the new calendar, but the original task in the original calendar is undeletable! Clicking "Synchronize" for the original calendar doesn't change anything!