Windows 11 KB5124008 Known Issues: Audio, Black Desktop, and RDS Bugs (Updated October 2026)

Windows 11’s September 2026 update (KB5124008) shipped the movable taskbar people had been asking for since 2021, plus fixes for two zero-day vulnerabilities already being exploited in the wild. It also broke audio, Remote Desktop, and more on a meaningful number of PCs. Microsoft has already shipped one emergency follow-up, KB5129195, that fixes some of it. Here’s exactly what’s broken, what’s fixed, and what to do if you’re affected.

Update, October 21, 2026: Microsoft has since shipped KB5127648 (released October 13), which resolves two of the issues below. A separate, newer Remote Desktop bug has also surfaced since this post was first published, caused by the later KB5124010 update rather than KB5124008 itself. The sections below reflect the current status of each issue.

Check Your Build Number First

Go to Settings > System > About. If you’re on build 26200.9445 or 26100.9445, you have the original September 8 update (KB5124008) without the emergency fixes below. If you’re on 26200.9457 or 26100.9457, you already have KB5129195, the September 15 out-of-band update that resolves several of these issues. Windows Update should have installed KB5129195 automatically, but it’s worth confirming rather than assuming.

USB Audio Failures (Partially Fixed)

Some USB Audio Class 1.0 devices stop producing sound entirely after this update. Device Manager shows the error “This device cannot start (Code 10)” on the affected audio device, and the Settings sound page can become unresponsive, which makes normal troubleshooting steps useless. Increasing the volume does nothing because Windows can’t start the device in the first place.

KB5129195 fixes a related but narrower bug where multichannel audio setups, like 3D audio or 8-channel configurations, lost sound entirely; it does not fix the complete device failure described above. If your device won’t start at all, wired USB audio is currently the more likely culprit, and Bluetooth audio devices have not been reported as affected. Uninstalling or disabling the device in Device Manager will not bring the audio back, since the fault originates in the update itself rather than the driver. Microsoft’s official Windows release-health tracker still lists this issue as “Mitigated” rather than resolved, last updated September 29, 2026, and says IT admins needing an immediate fix should contact Microsoft Support for Business.

Remote Desktop Services Breaking (Fixed)

After the September 8 update, some PCs couldn’t establish Remote Desktop connections at all, getting stuck at “Please wait for the Remote Desktop Configuration” or losing a responsive File Explorer and Management Console even after connecting. KB5129195 resolves this. If you rely on Remote Desktop and haven’t installed the emergency update yet, this alone is a good reason to check for updates now rather than wait for the next scheduled Patch Tuesday.

New Issue: Remote Desktop Fails for Non-Admin Users (Mitigated)

This is a different, newer bug from the Remote Desktop issue above — it was introduced by the September 22 preview update (KB5124010), not the original KB5124008. After installing KB5124010 or later, non-admin users on devices with Administrator protection enabled may be unable to connect via Remote Desktop at all, seeing the error “The token that was passed to the function is invalid” (error code 0xC000000D). Microsoft has only committed to a fix in a future update as of this writing; as a workaround, IT admins can temporarily turn off Administrator protection by resetting the User Account Control Type Of Admin Approval Mode policy in Intune or Group Policy.

Explorer.exe Crashes and Black Desktop (Resolved October 13)

A smaller number of PCs are seeing Explorer.exe fail to start or crash almost immediately after sign-in, leaving a black screen with no taskbar or desktop icons. So far this mostly affects enterprise environments using profile-management tools like Citrix UPM, FSLogix, Horizon, or ProfileUnity ProfileDisks, on both 24H2 and 25H2. KB5129195 (September 15) did not fix this, but Microsoft’s October 13 update, KB5127648, does. If you’re still on an earlier build, open Task Manager (Ctrl+Shift+Esc, which usually still works even with a black desktop), find or create a new task, and run explorer.exe manually to restore your desktop for that session — then install KB5127648 or later to stop it from recurring. The same October 13 update also fixes a related bug where apps requiring AC-3 (Dolby Digital) audio decoding would close unexpectedly or fail to launch, which started with the September 22 KB5124010 update.

File History No Longer Detects Backup Drives (Unresolved)

File History, the built-in tool that keeps versioned backups of your files on an external drive, has stopped detecting connected backup drives for some users after this update. Microsoft hasn’t officially confirmed this one yet, and KB5129195 doesn’t address it. If you depend on File History, don’t assume your backups are still running; manually check under Control Panel > File History that it still lists your drive and is actively backing up, and consider a second backup method in the meantime, since a broken detection step means new file versions may not be getting saved at all.

AMD Radeon GPU Instability (Unresolved)

PCs with AMD Radeon GPUs, including the RX 6600, RX 7700 XT, RX 7800 XT, RX 7900 GRE, RX 7900 XTX, and RX 9070 XT, have reported driver timeouts, black screens, and system freezes since installing this update, including outside of gaming. Rolling back to an older GPU driver has not resolved it for affected users, which points to the Windows update rather than the driver itself. KB5129195 explicitly does not fix this. If you’re on an affected card and haven’t installed KB5124008 yet, it may be worth waiting for a further fix before updating unless you need the September security patches urgently, in which case installing them and keeping an eye on Windows Update for a follow-up is the more realistic trade-off, since skipping security updates indefinitely carries its own risk.

Shared Folders in Linux Virtual Machines (Fixed)

Some apps that run Linux virtual machines under Windows using the HCS Plan9 file-sharing feature briefly lost access to folders shared from the Windows host, even though the virtual machines themselves started normally. This mostly affected developer tools and AI coding assistants that use a Linux VM behind the scenes. KB5129195 fixes it.

Why So Many Bugs in One Update?

September’s update patched roughly 974 vulnerabilities across Microsoft’s product line, the largest single-month total on record and a sharp jump from prior months. Analysts have linked the increase to Microsoft’s expanded use of AI-assisted vulnerability discovery in its own codebase, which is surfacing far more issues than manual review historically caught. More security fixes packed into one release naturally raises the odds that some of them touch code paths in ways that weren’t fully caught in testing, which is the most plausible explanation for why this particular update has had more fallout than a typical Patch Tuesday.

What NOT to Do

Don’t uninstall KB5124008 purely to avoid these bugs unless you’re already experiencing one of them and need immediate relief; doing so also removes the fix for two zero-day vulnerabilities that are already being actively exploited, which is a worse trade-off for most people than a UI change or an intermittent bug. Don’t assume every unrelated problem on your PC this month is caused by this update either; check whether your specific symptom matches one of the patterns above before spending time troubleshooting the wrong cause.

Related: Windows 11 September 2026 Update (KB5124008 & KB5124012): What’s New and What It Fixes · Microsoft Defender’s ShieldBreak and ShieldCrash Flaws Explained

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