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.
CANNOT_INSERT_UPDATE_ACTIVATE_ENTITY: DailyContact2: execution of AfterUpdate caused by: System.ListException: Duplicate id in list: 0014000000NcWknAAF Trigger.DailyContact2: line 12, column 1
Looks like your leads are trying to use the same SFDC ID. Try merging them in both systems first, or speak with SFDC Admin.