Most on-page audits catch the obvious stuff: a missing title here, a duplicate meta description there. The thing that quietly costs you rich results is structured data that exists but is invalid, and most flat-list crawlers either skip it or bury it. Here is why it happens and how to catch it.
Source: [Dev.to](https://dev.to/toolkitonline/your-structured-data-is-probably-broken-and-your-crawler-isnt-telling-you-20k)