Salesforce Sync Error: Unable to update Lead

I am getting this error during our sync to sfdc am runs, mostly every to every other day.

Our instance has lots of lead/contact dups between sfdc and marketo, which we are working on cleaning up, any insight here to what this error means and how I can get it fixed.

  Why: Marketo is unable to update Lead in Salesforce.

  Error details:

CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY: DailyContact2: execution of AfterUpdate caused by: System.ListException: Duplicate id in list: 0014000000NcWknAAF Trigger.DailyContact2: line 12, column 1

  Sample Leads: