Fantasy Flight Games found errors and omissions with their initial release of Mansion of Madness sets and has set up a page to help fix the problem.
From the announcement:
Last week, it came to light that our initial shipment of Forbidden Alchemy, the recently released Mansions of Madness expansion, contained some errors affecting playability.
We have now concluded an audit of this product and have prepared a full list of any found issues, along with accompanying errata, in the Forbidden Alchemy FAQ (pdf, 1.5 MB). FFG will offer free replacement parts to any customers affected by these errors.