HCM Person Analyzer fails to indicate problem with contacts

We were attempting to re-hire an ex-employee, and it was failing with message APP-PAY-07207 Mandatory value cannot be null.  We ran the HCM Person Analyzer on the record, and did a trace, in the expectation of needing to attach them to an SR, but the trace enabled us to pinpoint the cause, so we haven't raised one.  However, the Person Analyzer did not indicate the problem, which was in the Contacts table.  There were 4 rows on PER_CONTACT_RELATIONSHIPS, but one of them had a CONTACT_PERSON_ID for a record that did not exist on PER_ALL_PEOPLE_F (how the users managed to do