I told you that the Windows 11 August 2026 update could break certain games, reboot your PC out of nowhere, and cause other performance issues, including lower-than-usual frame rates. A gaming studio later flagged Windows 11 KB5121003 as the root cause, and Microsoft is now officially investigating the reports after a week of silence.

“Following the release of Windows updates on August 11, 2026 (KB5121003) and later, Microsoft received reports of issues involving inability to run games as expected,” Microsoft noted in a support document. “We are presently investigating to determine if this is an issue caused by Microsoft. We will provide an update when more information is available.”

The August 2026 update (KB5121003) rolled out on August 11, bringing the OS to Build 26200.9168 if you are on version 25H2 or Build 26100.9168 on PCs with version 24H2. I did not run into unexpected problems after installing the update, but that was until I played ARC Raiders, which would simply crash and reboot Windows.

Windows Latest’s investigation later found that hundreds of gamers had reported similar problems within a few hours, and multiple popular titles were affected, including:

• ARC Raiders
• MARVEL Tōkon: Fighting Souls
• The Finals

I’ve had reports of issues affecting other titles as well, but at this point, it’s confirmed that the above three games are affected. ARC Raiders and The Finals are developed by the same studio, Embark, which shared more details in a message posted on its Discord server.

“This is a crash related to the file inpoutx64.sys, which changed with the Windows update,” Embark noted in a Discord post. “We’re working towards a long-term fix, but in the meantime there is a workaround solution that will safely remove the file in question and allow you to play the game without issue.”

Windows 11 KB5121003 shipped with more than 400 security fixes and over 50 general improvements, so it’s possible that one of the changes broke compatibility with inpoutx64.sys, which is mostly used by third-party software or hardware utilities, such as Razer’s software for managing keyboard backlight settings.

Microsoft is now investigating Windows 11 KB5121003 issues

At this point, there’s strong evidence that Windows 11 KB5121003 is behind at least some of these gaming problems, as affected users say removing the update brings things back to normal.

Given the growing number of reports, Microsoft has now confirmed that it’s aware of the gaming issues and is investigating them. It’s also urging gamers to submit feedback using Feedback Hub so it can identify what actually changed.

While Embark has linked the crashes to inpoutx64.sys, we still don’t know what Windows 11 KB5121003 changed that broke compatibility with the driver, and that’s also something Microsoft is now trying to figure out.

This is a developing story….

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