It might be possible that some of the (contact) data in iController is not the same as the data in your accounting program.
The client sheet gets updated only when there are open invoices for the client.
An archived client won't have data imported in iController until there is an open invoice again.
- Day 1: You change the email address of client A in your accounting program.
- Day 2-3-4: The outdated email address is still visible on the client sheet.
- Day 5: Client A gets an open invoice.
- Day 5 after data export/import: email address has been changed in iController.