Windows 11 KB5121003 Problems: What Gamers and ARM64 Users Need to Know

Games affected after the update

Microsoft has acknowledged reports that a limited number of games may not run as expected after the August updates. The titles named in reporting and Microsoft’s release-health notices include ARC Raiders, MARVEL Tōkon: Fighting Souls, and THE FINALS. Symptoms reported by players include hangs, crashes, and—in some cases—unexpected system restarts. Microsoft lists the issue as Investigating for both Windows 11 24H2 and 25H2.

That status matters: Microsoft has confirmed the reports, but it has not yet published a final root-cause analysis or a general fix. The release-health pages say the company is still determining whether the issue is caused by Microsoft’s updates.

The suspected inpoutx64.sys conflict

Embark Studios, the developer behind ARC Raiders and THE FINALS, connected those games’ failures to inpoutx64.sys, an older third-party kernel-level port-access driver used by some hardware utilities. The current evidence points to a compatibility conflict between the updated Windows environment and systems where that driver is present—not a confirmed explanation for every affected game or PC.

Embark’s reported workaround uses Command Prompt to stop and remove the inpoutx64 service and driver. Because the driver may have been installed by a hardware-monitoring or control utility, deleting it can affect that utility. Users should first identify the parent software, check for an updated version, and use Embark’s current official instructions rather than copying commands from an unverified forum post.

The practical implication is that gamers who encounter crashes should check for inpoutx64.sys before immediately uninstalling KB5121003. Removing the third-party driver may resolve the compatibility problem while allowing the security update to remain installed, although the available evidence does not guarantee that outcome for every title.

Separate ARM64 problem: Teams and New Outlook may not launch

A different issue has been reported on Snapdragon-based ARM64 systems. Reports involving the Surface Laptop 7, with similar claims concerning the Surface Pro 11 and HP OmniBook 3, say that the new Microsoft Teams and New Outlook apps fail to launch or close immediately after KB5121003 is installed.

The reported failure appears narrower than a general ARM64 application problem. In the affected cases, Classic Outlook, Word, Excel, and other traditional Win32 applications continued to work, while the newer Teams and Outlook packages distributed through MSIX or AppX did not.

Troubleshooting reports include an AppModel Runtime error, 0x80073CFC, and a DependencyIssue status for New Outlook. Users reported trying repairs, resets, re-registration, and reinstalls without resolving the launch failure. In those reports, uninstalling KB5121003 restored Teams and New Outlook. These observations come from user and administrator reports, not from a published Microsoft root-cause analysis.

Microsoft has not listed the ARM64 issue on its health dashboard

Microsoft’s Windows 11 24H2 and 25H2 release-health pages currently list the game-unresponsiveness problem as under investigation. They do not list a corresponding Teams or New Outlook launch issue for ARM64 devices. That means there is no Microsoft-published mitigation, safeguard hold, or repair timeline for the app problem in the available status information.

The absence of a dashboard entry does not disprove the reports; it means the issue has not been formally documented there. Organizations should therefore treat the ARM64 reports as a potentially real but not yet broadly validated compatibility problem.

The security cost of uninstalling KB5121003

Skipping or removing the update is not a risk-free workaround. August 2026 Patch Tuesday addressed more than 400 vulnerabilities, although security researchers report slightly different totals depending on how advisories and related fixes are counted. CrowdStrike counted 415 vulnerabilities, while other reporting put the total closer to 400.

The release also fixed CVE-2026-68820, an elevation-of-privilege vulnerability in the Windows Ancillary Function Driver for WinSock that was reported as actively exploited. The update addressed other zero-day vulnerabilities as well, including CVE-2026-62832, the flaw known as “LegacyHive.” Available reporting distinguishes LegacyHive from CVE-2026-68820: LegacyHive was publicly disclosed, while CVE-2026-68820 was the vulnerability identified as actively exploited.

What users should do

• If the PC is unaffected: Keep KB5121003 installed and continue monitoring Microsoft’s release-health pages.
• If a listed game crashes: Check whether inpoutx64.sys is installed, identify the utility that uses it, and look for an updated or removable version before uninstalling the Windows update.
• If Teams and New Outlook fail on an ARM64 PC: Record the Windows build and AppModel errors, try the organization’s approved recovery process, and consider temporary removal only if the application failure blocks essential work.
• If the update is removed: Treat that as a short-term operational workaround, minimize the device’s exposure, and reinstall the security update when Microsoft or the affected software provider publishes a compatible fix.

For most users, retaining KB5121003 is the safer default because of the actively exploited vulnerability it fixes. The exception is a system where the update causes a documented, work-stopping failure and no alternative workaround is available. Even then, the decision should be temporary and followed by monitoring for an official repair.