I'm using v 10.6.9 app on Mac OS v 11.1 [Big Sur] on 2019 Mac mini and also on 2020 MacBook Air. I have had the 'blank notes' every few days including today Jan 31,2021. a close then open of the app restores views of all notes.
the app has fixed it every time, but still takes time and is a concern that data may have been lost.