I have 10.39.7, and I’ve just started seeing this problem in the past couple of days. Restarting Evernote hasn’t helped.
The first time I saw it, a set of three bullet points disappeared from a note within a day or so after I wrote them. I wrote them again, and they disappeared again. The third or fourth time that I wrote them, they stayed. But it was very frustrating.
The second and latest time I’ve run into the issue was today. This time it wasn’t bullet points—it was a couple dozen brief text paragraphs. I wrote them last night (at the end of an existing Evernote document), and today they’re gone.
In both cases, I checked the note history but Evernote had no record of the changes that I had made.
Really concerning—now I don’t know whether anything I type will disappear.