I have experienced the same problem.
previous feature updates have applied without issue.
no files were found in my documents folder after the upgrade.
they could not be found in the windows.old folder
rolling back did not restore them
they cannot be found in one drive.
I am lucky that I store my documents on backed folder on the LAN, but kept a local copy of a number of files for when I am offlline.
I have lost some work from this and lost a few hours today trying to figure out what happened.