There's plenty of cases where new users add every movement of a concerto, sonata, or whatnot with the type "concerto", "sonata", etc. That's pretty much never correct. Since songs aren't usually marked as part of songs, it should be pretty safe to have a report that looks for all works of type X that are part of another work of type X - most of those if not all will need fixing. Different types are perfectly legit though (aria as part of opera, or song as part of song cycle, etc).