I run a nightly import/update for all of my organizations.
I have a field called Source ID and this field is set for the key binding so that it does not create duplicate records for the same organization.
Recently I started to "block" some old outdated Organizations that no longer exist within my company, however we still keep them in our records for history purposes. When I block them they no longer show up in the list for service calls, this is good, that is what we wanted.
The problems is, when the nightly import/update runs it creates a new organziation record with the same Source ID number. So, now duplicate records are getting created for all of the Organizations that I have blocked. Why is this? If I unblock the organization, it does not get duplicated.