Last Wednesday's rollout of KB3194496 to Windows Insiders, which is a Cumulative Update to build 14393.222 for Windows 10 PCs, impacted a "subset of users" who were unable to complete the upgrade, and have since been stuck in a install loop when rebooting their machines. Microsoft hasn't said much beyond acknowledging the issue, and seemingly ignored Windows Insiders who reported the failed upgrades well before the Cumulative Update was made available to the public last Friday.
Fast forward to today, and Microsoft has now posted a message in the, as of writing, 30 page topic stating that they are working on "finalizing" a fix:
We’ve been working diligently on this issue and are finalizing a clean-up script that will fix the underlying issue preventing the install of KB3194496 (Cumulative Update 14393.222) for affected users. Your patience during our research and subsequent work is greatly appreciated.
Thank you as always and stay tuned!
It would seem that Microsoft will be rolling out a 'clean-up script' to fix the issue the prevents the upgrade from completing. In the support forum topic, many people have come up with different workarounds to complete the upgrade, but almost all require registry editing or having to reinstall Windows 10 over the failing update.
We found one solution that seems to have helped a number of people, but this also requires registry editing. Now that Microsoft appears to be in the final stages of testing the clean-up script, our advice is to wait for the company to roll out that fix.
It isn't clear how the fix will be handled, but given that non Insiders are also experiencing the issue, we expect this will have to be rolled out through Windows Update.
Update: Microsoft issued the following statement to Neowin:
We are aware of an issue with the recent Windows 10 cumulative update that impacted a small number of customers in the Windows Insider Program that were running a previous build of the OS. We expect to have a solution in place for these customers soon, and will be communicating with Insiders via the Feedback Hub.