I am also having problems with search since updating to 6.13.3.
I enter a keyword that I know yielded correct results in previous versions of the app, and now it doesn't return any results. If I enter the same search keyword in the web app (evernote.com), I see the correct results.
Definitely something broken with search the 6.13.3 Mac upgrade. I can no longer trust the search results in the Mac app, so I've stopped using it and am only using the web app now.
Keep in mind, I depend on search results, or the absence of search results, as important information. For example, I search the Evernote Mac app for the title of an important document from years ago. If I find no search results, I assume that I never uploaded the document to Evernote. So now I waste time searching in other locations for this document, or for a paper backup. I would have wasted even more time were I not suspicious of a bug and searched the Evernote web app.