Microsoft hasn’t exactly had the best track record when it comes to Windows 10 updates, and that was readily apparent with the release of the Windows 10 October 2018 Update. Unfortunately for Microsoft, some users are experiencing problems with the System Restore feature after installing a Windows 10 update.
Microsoft describes the scenario where users may encounter issue. Let's say that you create a System Restore point labeled, for example, May 15th, and you go about your business as usual. You later install "one or more" Windows 10 updates. Then for whatever reason, you need to go back and attempt to recover the May 15th restore point.
It's at this point that Microsoft says that the save restore point is not recovered, and that users instead are greeted with a Stop error (0xc000021a). Then, once you restart your computer, it unfortunately can no longer boot into the Windows 10 desktop.
Microsoft describes what is happening behind the scenes, writing:
During the system restore process, Windows temporarily stages the restoration of files that are in use. It then saves the information in the registry. When the computer restarts, it completes the staged operation.
In this situation, Windows restores the catalog files and stages the driver .sys files to be restored when the computer restarts. However, when the computer restarts, Windows loads the existing drivers before it restores the later versions of the drivers. Because the driver versions do not match the versions of the restored catalog files, the restart process stops.
If you find yourself a victim us this epic fail on Microsoft's part, the company fortunately has a workaround to ease your pain. You'll need to enter into the Windows Recovery Environment, and navigate to Troubleshoot --> Advanced options --> More recovery options --> Startup settings. Next, select Restart now.
Within startup settings, you'll want to enable Disable driver signature enforcement. Microsoft notes that hitting the F7 key might be required to enable this setting. Once all of these steps are taken, you should be able to restart Windows 10 normally with your previously selected restore point activated.
Microsoft says that you can avoid this problem in the future -- at least until it has implemented a suitable fix -- by restarting your computer to boot directly into the Windows Recovery Environment and then start the System Restore process from there instead of the native Windows environment.
For more detailed information on this issue and the workaround, be sure to check out this Microsoft support article.