Review Funnel loading circle disappears and reviews don't download

Very infrequently I have a customer who can't download reviews from the Review Funnel. It usually happens with non-english reviews. If you click the Download button and it disappears and nothing happens.

Open up a Console window, by right-clicking > inspect > look for the console window. Check it for messages like so...

In this one you can see a database error on the meta_data field. This fix is to change the collation on the database column. 

Usually it is the review title or review text fields as well that have trouble with characters.