Just experienced this yesterday for the first time (at least that I know of). Have been upgraded to Win 10 since release day, I wrote a sentence in the desktop version of OneNote 2013 that just kept disappearing - over and over. Then I noticed several lines above had shifted left outside of the left margin. Pretty bizarre, not to mention being an annoying PITA! THIS IS MAKING ONENOTE UNUSABLE AND UNRELIABLE! And it's the main reason for using Windows for me.