Rescheduling tasks in Calendar view

I use the Calendar view to reschedule overdue tasks. If I drag a task scheduled for last week from the Overdue box to the Planned for This Week box, I get the following warning flashing up in yellow (Action set for a future date:week 43). The task then disappears from the calendar view. I can find the task using search but I cannot get it to appear in the Calendar view. However if I drag the task to the “this week” or “next week” boxes on the right hand side the task is rescheduled correctly.

I am sure this worked correctly last week as I have used this function regularly.

Thanks

Steve
Any thoughts