When I query the OpenFDA API, some queries which should be valid yield invalid results. I suspect this has to do with an error in how forward slashes are handled in queries on the FDA server (which appears to be fronted by nginx).
For example, say I am searching for the number of times a Hepatitis C Virus NS3/4A Protease Inhibitor was associated with an adverse event. That link is to a query on "Hepatitis C Virus". It shows me that "Hepatitis C Virus NS3/4A Protease Inhibitor [EPC]" should be a valid search term.
However, if I search for that term, I get an error. In fact, any query that I have tried without a forward-slash ("/") works fine, while any query that I have tried with the forward-slash fails in the same way.