Dropbox search is broken and it doesn't show the correct results.

I have uploaded a folder directly of files, where (public domain) books are organized in folders by author, and then as files for each book.

I had evidence that a certain quote existed in the folder directory for a certain author. Emphases added for point of discussion later: 

The gulf which has long yawned between employers and employed is widening; and the distance between the avenues and the tenement houses is constantly becoming greater."

😀 When I search for “avenues”, I first find the right book (file), and then within the file I find the specific paragraph.

😡 When I search for “tenement”, Dropbox tells me there is no such text in the directory. (I have since downloaded this plain text file, and Microsoft Word can find it easily).  This has happened a couple of times, where I have evidence a quote exists, and I search using the Dropbox system, and it doesn’t find it. My very vague impression is that this is a new behavior? 

😡 When I search for “employer”, Dropbox gives me all sorts of files, specifically highlighting in several of the cases that it has found “employment”. This is completely unacceptable, and if you are doing soft searches, it only wastes your CPU cycles. 

I have screen-grab proof of all of the above, if it helps to see.