Two shows came back as similar and made no sense together, so I went into the data. They shared four crew members and all four were casting directors from the same office. One casting director works across many shows, so a shared casting credit creates a connection that carries no information.
So I excluded those jobs before comparing crew.
A couple of shows whose only link was a shared casting office now show no match at all. A blank is better than a wrong one.
I think I nailed it.
For a more in-depth explanation, read this ADR.