It's been while -- at least a few days -- since Microsoft released a problematic update for Windows 10, so we were probably about due another one. And sure enough, this week's KB4532693 update is causing issues for people.
https://betanews.com/2020/02/13/windows-10-kb4532693-lost-user-profile/
https://betanews.com/2020/02/13/windows-10-kb4532693-lost-user-profile/