You see this message typically when you have done a back up and restore in Console and it's where the Booking ID generated from Console has restarted from an earlier ID so you have 2 bookings linked to the same Console Booking ID.
To fix this issue you need force the booking to retrieve a new Booking ID from Console.
To do this check the Unlink box in the booking > Save Changes.
NB. You will need to allow 5 minutes for an owner booking to update to Console.