There is no rollback feature for the no-code connectors.
If the connector succeed to fetch and parse the complete dataset (JSON, CSV, etc.), the index is updated. In the connector debugger, the run is marked as "Success".
If the connector does not succeed (cannot fetch the field, data is not correct, etc.), the index is not updated and nothing is changed. In the connector debugger, the run is marked as "Failed".
That being said, if it's failed, you should be able to see specific error message returned in the connector debugger which would allow you to troubleshoot the tasks further.