I am running WIN 10 on a desktop PC and as of Monday I had all the current release updates installed (Not an insider on this PC)
Tuesday night I used the "check for updates" and walked away.
This AM I had an error message. I selected the "Fix issue" radio button and got an error message "windows 10 couldn't be installed. You can't install windows on a USB flash drive using setup"
I have NO USB flash devices installed, only a USB mouse/keyboard.