Microsoft: KB5120998 Mouse Reset Bug Confirmed to Affect Only Non-English Windows 11 PCs

Microsoft has officially confirmed that a recently identified bug, introduced with the KB5120998 August 2026 preview update, which causes user-configured mouse settings to revert to their default states, exclusively affects non-English versions of Windows 11. This clarification comes after a number of users reported experiencing unexpected alterations to their mouse preferences, including pointer speed, sensitivity, and button configurations, immediately following the installation of this specific preview update. Microsoft has explicitly stated that English language installations of Windows 11 are not impacted by this particular issue, narrowing the scope of the problem significantly.

The KB5120998 update, released as a preview in August 2026, was intended to offer Windows 11 users early access to a collection of upcoming fixes and enhancements designed to improve system stability and functionality. However, shortly after its general availability to those opting for preview builds, a segment of the user base began encountering the aforementioned mouse settings reset. This unexpected behavior necessitated users to manually reconfigure their mouse preferences each time the update was applied, leading to considerable inconvenience and potential disruption to daily workflows, especially for users who rely on specific, finely-tuned mouse settings for productivity or accessibility.

Following an internal investigation, Microsoft's engineering teams have determined that the root cause of this mouse settings reset is intrinsically linked to the localization files and language packs utilized in non-English versions of Windows 11. This suggests that the underlying code responsible for managing and preserving user-specific preferences interacts differently with these localized components compared to the English version. The company has not yet provided a definitive timeline for the release of a permanent fix, but it is anticipated that a resolution will be incorporated into a future cumulative update for Windows 11. In the interim, users operating non-English versions of Windows 11 who are experiencing this issue are advised to temporarily refrain from installing the KB5120998 preview update until a comprehensive solution is deployed by Microsoft. Alternatively, affected users may need to reapply their preferred mouse settings after each installation of the problematic update. Microsoft's official support channels remain available for users seeking further assistance or to report similar technical difficulties. This incident underscores the inherent complexities involved in developing and deploying software updates across a diverse global landscape of languages and regional configurations, emphasizing the critical importance of rigorous and comprehensive testing across varied environments prior to widespread release.