The Delete from Model stage has two optional outgoing ports to which you can attach various sink stages. One sink captures data for the successfully deleted entities and relationships, while the other collects any records that the dataflow did not process correctly. This is called the Error Port, and records that pass through this port into the sink are considered malformed.
Capturing malformed records can help you identify the problem with those records. When you attach a sink to the Error Port, the resulting output file will contain all the fields from the malformed records. It will also contain a Reason field that specifies why the record failed.