After a few days of the release of Windows 10 version 1809, plenty of users reported that it was somehow deleting users' data. It is some bug that affects only certain customers, nevertheless this is an extremely serious issue that is not acceptable even if it affects a small number of users. Microsoft has started an investigation, so Windows 10 version 1809 has been temporarily pulled from their servers. It is not available for download any more for now.
There is a new note in the 'Known Issues' section of the Windows 10 October 2018 Update History page:
We have paused the rollout of the Windows 10 October 2018 Update (version 1809) for all users as we investigate isolated reports of users missing some files after updating.
If you have checked for updates and believe you have an issue, please contact us directly at +1-800-MICROSOFT or find a local number in your area https://support.microsoft.com/en-us/help/4051701/global-customer-service-phone-numbers.
If you have access to a different PC, please contact us at https://support.microsoft.com/en-us/contactus/
If you have manually downloaded the Windows 10 October 2018 Update installation media, please don’t install it and wait until new media is available.
As of this writing, the entire OS family, including Server builds and Internet of Things (IoT) version, are removed from Windows Update and other servers. The Media Creation Tool has been pulled too.
It is worth mentioning that Windows 10 version 1809 was the first feature update for which Microsoft skipped the Release Preview ring. It could have helped to catch the issue before the OS was made available to the general public. Unfortunately, this didn't happen.
This particular issue was actually reported well in advance on the Windows Insider Hub by several Insiders but since it was not a widespread problem before it became publicly available, it was not fixed.
Even if you are very eager to install the most recent version of Windows 10, I recommend you to wait for fixed media where the issue should be resolved. There are also other bugs reported with the final build, such as the Task Manager not showing correct CPU usage for some apps, Intel driver incompatibility which made the OS unstable, and internet connectivity being affected if IPv6 was turned off. Surprisingly, this release of Windows 10 was also supposed to be offered to the Long Term Servicing Channel (formerly LTSB). Now it seems Microsoft may have to do more extensive testing and fix all the serious bugs before deploying the OS again.