Windows 11 KB5074109 problems deepen as Microsoft ships emergency update

Microsoft just pushed out another emergency Windows 11 fix, and it’s clearly aimed at cleaning up the mess from January Patch Tuesday. The company has released KB5078127, an out-of-band update meant to address problems tied to the January 2026 Windows 11 security updates, which have triggered a steady wave of complaints. 

What KB5078127 is supposed to fix

The biggest targets are Outlook Classic and apps that depend on cloud-stored files. Earlier January updates caused Outlook and cloud-backed apps, such as OneDrive and Dropbox, to behave unpredictably or stop working properly for some users, and KB5078127 is intended to restore normal behavior. 

The patch has also been described as addressing Outlook Classic POP/PST scenarios, particularly cases where mail archives are stored in cloud folders.

KB5074109 rollback is failing for some users

Complicating things further are rollbacks: some Windows 11 users trying to remove KB5074109 are running into error 0x800f0905, a servicing stack/component store issue that can block the uninstall completely. That leaves affected PCs in a rough spot... either live with an update that’s causing app and sleep problems, or move on to more involved repair steps. 

Why this matters: January’s update cycle is still unraveling

This isn’t a minor quality-of-life patch. January’s Windows 11 update cycle has been unusually disruptive, with multiple regressions and enough user impact that Microsoft has already had to ship fixes outside its normal schedule. Windows Central is calling KB5078127 the second emergency out-of-band update released in response to the chain reaction

Who should install it?

If you were hit by the January issues—especially Outlook Classic instability or cloud-file app problems—this update is clearly aimed at you. Microsoft is also pushing it broadly via Windows Update, so some people may see it offered even if they haven’t noticed issues yet.

What’s still unclear

KB5078127 likely won’t close out every KB5074109-related complaint overnight. Separate reports are still tracking issues across the January patch family (including rollback headaches), and it may take another cumulative update before everything fully settles.