After pausing the October update for Windows 10 to investigate reports of missing files from some users who upgraded their PCs, Microsoft believes it has found and fixed the problem. You still can't download it though, not unless you're a member of Microsoft Windows Insider program.
"Today we take the next step towards the re-release of the Windows 10 October 2018 Update by providing the updated version to our Windows Insider community. We will carefully study the results, feedback, and diagnostic data from our Insiders before taking additional steps towards re-releasing more broadly," Microsoft stated in a blog post.
The October 2018 Update caused a headache for some users who noticed that their personal documents went missing after upgrading their PCs. Even worse, rolling back the update, as some technical support staff suggested at the time, did not restore the deleted files.
Microsoft responded by pausing the update and asking anyone affected to contact the company directly.
While discovering that an update has deleted files is annoying in and of itself, even more frustrating is that this was a known issue in one of the earlier test builds in the Insider program. Microsoft thought it had a handle on the situation, but obviously did not.
Microsoft traced the bug to a feature called Known Folder Redirection (KFR). This lets users move known folders such as C:\Users\<Username>\<folder name> to a new folder location, such as somewhere on a secondary D:\ drive.
"In previous feedback from the Windows 10 April 2018 Update, users with KFR reported an extra, empty copy of Known Folders on their device. Based on feedback from users, we introduced code in the October 2018 Update to remove these empty, duplicate known folders," Microsoft said. "That change, combined with another change to the update construction sequence, resulted in the deletion of the original 'old' folder locations and their content, leaving only the new 'active' folder intact."
Microsoft identified three different scenarios in which applying the October update could result in deleted files, and says it has fixed all three. In total, the company says only one one-hundredth of one percent of those who installed the update reported any data loss.
While the issue is supposedly fixed, we recommend backing up your important data before applying the update, once it resumes to the public.