When I first reported this issue, many notes appeared blank/empty in both Windows-app and Web-app,
but later when I browsed my damaged (?) notes they "re-appeared" in the Web-app (using a Chrome browser, Windows 10) temporarily getting a new Edit-date.
After that (viewing the note in Web-app) the "damaged note" then appeared ok in the Windows-Evernote-app, again temporarily getting a new Edited-date but soon getting its old edit-date back.
So after flipping through all my notes in the web-app, all my (42) notes are now ok in all apps!
A bit bothersome, but I'm happy that I lost no data.