Marketo creating duplicate Lead records when a Contact record is already synced.
This happens when a Smart Campaign using the Sync Person to SFDC flow step qualifies a SFDC Contact record and attempts to assign the record to a Queue in Salesforce. When a SFDC Contact runs through the Sync Person to SFDC flow step, since Salesforce does not allow "Contacts" to be assigned to Lead Queues, Marketo will create an intentional duplicate "Lead" record in Salesforce and add the new Lead record to the queue.
If you want to prevent this behavior in your Smart Campaigns, add the filter "SFDC Type is not Contact" to the Smart List. This will disqualify SFDC Contact records from the campaign.
Another option: Add Choice options for the Sync Person to SFDC flow step and have the first choice be SFDC Type is Contact Do Nothing. This will cause SFDC Contact records to Do Nothing for the flow step but Lead or Marketo only records will process normally.
Who This Solution Applies To
Customers integrated with Salesforce