Windows update fail.

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Microsoft has finally fixed the issue “where some devices might enter BitLocker Recovery after updating boot files.” That left frustrated PC owners hunting for recovery keys after installing the April security update. The bad news is that Microsoft warns the fix itself might now fail.

The Windows maker released KB5089549 on May 12, but just 72 hours later it warned of a known issue where the new “security update fails to install with error 0x800f0922." This is likely down to memory availability. There are workarounds — but the best advice is to restart Windows.

“This issue occurs on devices that have limited free space,” Microsoft says. The security update likely fails “during the restart phase at approximately 35–36% completion,” and users may then see the message: “Something didn’t go as planned. Undoing changes.” The error code is 0x800f0922.

You can “allow the update to install by modifying an ESP registry setting,” but you’re warned that “editing the registry incorrectly can cause serious system problems.” That means backing up the registry first. Unless you’re very confident in doing this, do not attempt this workaround.

The better alternative is to “mitigate the issue by using Known Issue Rollback (KIR).” Your PC might actually do that for you now, undoing the update once it fails. As such, users are also told that “restarting your Windows device might help the resolution apply more quickly.”

This update is critical as June’s Secure Boot deadline approaches. Certificates first issued in 2011 will expire for the first time and must be replaced. May’s update brings “increased coverage of devices eligible to automatically receive new Secure Boot certificates.”

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While KB5089549 “includes the latest security fixes and improvements,” the BitLocker fix is just as critical. As is the Secure Boot update. The restart advice to accelerate a rollback is important for affected PCs. It’s a real world test of Microsoft’s recent improvements to Windows updates.