this update is a disaster causing everyone here multiple problems. uninstall fixes it but I've spent over a day fixing corrupted pst files for me and some others.
Microsoft's troubled Windows 11 KB5074109 January 2026 update is now under investigation for causing UNMOUNTABLE_BOOT_VOLUME boot failures on some systems. Affected PCs refuse to start and must be recovered via WinRE, adding a serious new symptom to an already messy Patch Tuesday.