I have 5 PC's , 4 of them serving as backups. I've done scores of Windows patches over each of them for years, with no notable issues-until now. The upgrade has been done to 2 of my PC's, with issues observed on one, my workhorse PC. So I'm not sure how generalizable the issue is.
But I noticed some 3 cloud backup products, plus a scheduled task was complaining about permissions or missing files. Long story short, I discovered a \users\[username] and a users\[username].000 archive directory. The former seemed to be an incomplete directory of 3 folders (one an AppData folder. The latter was my original user directory, including the root directories for two of my cloud backup solutions. This is more complicated than it sounds, because I maintain key application files in the cloud backup folders as well as a scheduled task bash script.
The cloud backup solutions with root directories handled the issue differently; one gave me the opportunity to redefine the path to the root (my preferred option); the other client (for a very well-known cloud vendor) simply aborted after alerting me to the "permissions" issue. Searching on the vendor website said you can redefine the path--but that implied your client was up and running. Great-did that mean I would have to resort to hacking the registry?
I filed a problem ticket with the vendor and faced the usual bureaucratic nonsense. First, they are obsessed with bookkeeping procedures, such as my PC's computer name (I've done installs on backup PC's for obvious reasons); second, they resort to procedural scripts, like if you're running their latest and greatest client software. (This product pushes client updates to PC's.) This is after I fully explained the nature of the issue in the write-up.
In the meanwhile, I implemented an old Unix shell game workaround which seemed to resolve the immediate problem (the cloud client software started up successfully), and I've made adjustments to hard-coded paths in scripts. It's not worth my time and effort to follow up on that problem ticket.
Not sure why the Windows update seemed to stop in the middle of updating/migrating my user folder, but I'll keep an eye on that issue in future updates.
