In case we need inspiration
One agency bought info from the Dems. That same info was given to another agency. They checked with the first one: check!. Basically, 17 agencies circle-jerked each other based on the same Dossier.
Regardless of exact number of agencies, the fact remains that they verified their information by consulting another agency that had the same faulty information that was produced by one agency, bought by another agency and shopped around to all the other agencies.