We have sync error because a record of value cannot be created because it already exists in the destination system.
However on our Salesforce account we have dublicate warning on. There is also dublicate block which is off. We think that Hubspot will handle (incorrectly) both warning and block same way.
I´m not referring that. These contacts doen´t even appear on this sync error list. But if we take a look contac record and Salesforce sync we will see there the error message.