I tried Thomas TKH's suggestion and, by itself it didn't work.
I tried formatting as FAT32 and NTFS
It didn't work (downloaded 100%, verified 100%, but failed around 50%)
I ran it as admin - it didn't work.
Here's what FINALLY WORKED!:
- I moved the USB drive to a different USB port
- I quick formatted it as NTFS
- I named it ("Win10"). Previously I was leaving it blank.
- I disabled Windows Defender antivirus
- I copied the installer and ran it as admin from the USB drive itself (as Thomas TKH suggested)
- After kicking it off, I closed all browser windows and File Explorer windows (including the USB drive that was open so I could run the app) and 2 or 3 lightweight background apps
I don't know which of the above was the turning point, but after doing all of them at the same time, it finally worked for me.
:-)