Check for duplicates based on email address is enabled but we have an issue

Check for duplicates based on email address is enabled but we have an issue

Hi, 

I have turned on the check to prevent duplicate leads from being created based upon email address. 

The issue is that we have lead edits that happen automatically based upon form completion on our website. 

If a customer name differs from the existing lead in Zoho CRM,  but the email address is the same, the old name gets updated, but the Notes attached to the old name are deleted, which is not good. 

How can we fix this?