Microsoft has confirmed that the newest Windows Canary build has a hard time shutting down in specific scenarios. According to Jen Gentleman (via @XenoPanther on Twitter), a member of the Windows engineering team at Microsoft, build 25314 and 25324 can hang when the user attempts to turn off the system with an Xbox Wireless Controller paired via a USB cable.
The message from Jen was published in the Feedback Hub (clicking the link will launch the Feedback Hub if installed) under a report about the shutdown not working after upgrading to builds 25314 and 25324. Interestingly, the same bug causes green screens of death for some insiders when their PCs are asleep.
Thanks for taking the time to report this - we"re investigating an issue where if you have a wired Xbox controller connected then shutdown will hang. This is the same root cause as some insiders seeing bugchecks (or rather green screens) when the PC is asleep. We"re working on a fix.
If your computer is affected by the bug, try disconnecting your controller before turning off the PC. As a reminder, keep in mind that Canary builds may be highly unstable since Microsoft is using the Channel to trial early long-term platform changes. Switching to Dev, Beta, or Release Preview may be a more reliable option, with the ability to test feature updates before Microsoft pushes them to the general public. Unfortunately, there is no easy way to go "down" from Canary to more stable builds, so reinstalling the operating system is your only option. For that reason, Microsoft started offering Windows Insiders free USB thumb drives.