Gmail Tasks Error

I recently transferred my EmClient account to a new laptop, and changed from POP3 to IMAP as part of the move.
My emails have moved without problem, but there is an issue with Tasks. I tried to Export/Import my Tasks but it wouldn’t work. I keep getting an error with the message “[Google Calendar] Maximum allowed due year is 2999”. The Properties says there are 2 tasks in the folder, but the Tasks window says “There are no tasks to show in this view”.
I’ve tried “Repair” but this doesn’t work, so what should I do next?