Windows 11 26H2 causes mixed language UI and Windows Hello/PIN issues after upgrad

Hello,

We are seeing multiple issues after upgrading Windows 11 devices to Windows 11 26H2.

The same behavior has been observed across several managed customer environments, and I also experienced it on my own PC.

Symptoms observed after upgrading to Windows 11 26H2

• Windows Hello / PIN stopped working correctly or required reset/re-registration.

Parts of the Windows UI changed to a mix of Norwegian and English, even though the Windows display language remained set to Norwegian.

Some third-party software also reported compatibility issues after the upgrade.

The affected devices are managed in different ways, including Microsoft Intune.

On the affected PC, the upgrade resulted in:

• Windows 11 Enterprise
• Version: 26H2
• Initial build: 26300.9457

Language issue and KB5127648

After installing:

KB5127648 – 2026-10 Security Update

the system was updated to:

Build 26300.9711

After this update, the mixed Norwegian/English language issue disappeared.

I also checked the CBS logs. At approximately the same time as KB5127648 was installed, multiple nb-NO language components were updated. Older Norwegian language packages were marked as superseded, and newer packages with version 10.0.26100.9711 were installed.

For example, the CBS log showed entries such as:

Runlevel-Win0-Package~31bf3856ad364e35~amd64~nb-NO~10.0.26100.9711 State changed to: Installed

and:

Runlevel-Win2-Package~31bf3856ad364e35~amd64~nb-NO~10.0.26100.9711 State changed to: Installed

This strongly suggests that KB5127648 updated Norwegian language resources that were affected after the 26H2 upgrade.

Windows Hello / PIN issue

We have also seen Windows Hello / PIN issues after the 26H2 upgrade on multiple devices.

In at least one environment, PIN reset functionality started working again after recreating/reconfiguring the Microsoft PIN Reset Enterprise Applications and reapplying the required admin consent.

Questions

Is Microsoft aware of a Windows 11 26H2 issue where the UI becomes a mix of English and the configured display language after upgrade?

Is the language-related fix included in KB5127648, even if it is not explicitly listed in the published release notes?

Is Microsoft aware of Windows Hello / PIN reset issues after upgrading to 26H2?

Are there any recommended mitigations or known fixes for affected enterprise devices?

1. Is there any known difference in behavior depending on whether the upgrade is delivered through Windows Update, Intune, or 3rd party patch management?

This issue has been observed across multiple managed environments and is not limited to a single device or management platform.

Any confirmation from Microsoft would be appreciated.Hello,