Some words not found in some documents

Hi

First of all, thank you for this great plugin!

I’m installing this plugin in a client’s site, and when testing it, sometimes there are words that I know exist in a certain attached document, but that file is not returned in the search results (however, other files in which the word exist, are returned).
And it’s not that the document isn’t indexed, because it is returned in other search results.
To be fair, I tested this also on the public URL supplied by CSE and the results are the same – said file doesn’t appear.

So while this apparently isn’t a problem with the plugin itself, I was wondering if you’ve run into this bug and might know the cause of it and/or how to handle it. Any help is appreciated.
The site is in Hebrew, if that makes any difference.

Thanks!