I am 100% sure that the disabling of tracking has nothing to do with the failed record creation in SFDC.
Some smart campaign are adding the record type ID to the record before it's inserted in SFDC. And this Smart campaign is apparently doing the wrong thing.
Look at the activity log of the failing record, and focus on the (absence of) data value change for the record type field, it should tell you from which smart campaign the problem is coming.
If I was to put money on your issue, I would bet you are setting a contact record type ID to a new records, which can only be created as a lead.