This goes for Logos and Verbum, Mac only (doesn't happen on Windows), Mac running Sequoia 15.0 and the beta Logos (I know beta is not fully released but have been using beta for a number of years and never had this issue).
I have a note attached to each day in the three year lectionary (RCL Daily). When I hover over the note icon, the popup shows the text. When I click on that to open the note, once in a while the note appears but if I move the note the text disappears, and usually when I open the note, it does not display any text (which I know is still there).