Windows bugs and fixes September 20 2026: status
Chapters
Which Windows fixes have shipped?
KB5129195 fixed Remote Desktop failures and only part of USB audio, TechSpot reported on September 15, 2026.
The shipped Windows update fix covers Windows 11 24H2 and 25H2, where TechSpot said on September 15, 2026 that KB5129195 repairs Remote Desktop Services instability, a Host Compute Service virtualization failure and multichannel audio on some devices.
TechSpot also reported on September 15, 2026 that Remote Desktop trouble could produce connection and sign-in failures, while Microsoft Management Console, RDS Licensing Diagnoser, File Explorer and the Windows Update page could stop responding. Apps running Linux virtual machines through Host Compute Service could lose access to local files, according to the same TechSpot report published on September 15, 2026.
I separate those shipped repairs from the Windows known issues that remain open. TechSpot reported on September 15, 2026 that KB5129195 restores 8-channel and 3D modes on some USB devices, but does not repair every start, sound or volume-control failure.
| Problem | Status | Named update | Source and date |
|---|---|---|---|
| Remote Desktop connection and sign-in failures | Fixed | KB5129195 | TechSpot, September 15, 2026 |
| Host Compute Service virtualization failure | Fixed | KB5129195 | TechSpot, September 15, 2026 |
| USB audio in 8-channel or 3D mode | Partly fixed | KB5129195 | TechSpot, September 15, 2026 |
| Domain trust and valid-credential sign-in failure | No permanent fix shipped | Workaround only | BleepingComputer, September 17, 2026 |
TL;DR
Windows 11 domain sign-in broke after KB5124012, BetaNews reported on September 17, 2026, while USB audio broke after KB5124008 and KB5124012, BleepingComputer reported on September 14, 2026. KB5129195 has fixed Remote Desktop failures, virtualization trouble and some multichannel audio failures, but domain authentication and some USB Audio Class 1.0 failures remain unresolved, TechSpot reported on September 15, 2026.
- KB5129195 repairs Remote Desktop failures and part of the USB audio regression, according to TechSpot on September 15, 2026.
- No permanent domain-login fix has shipped, according to BleepingComputer on September 17, 2026.
- Disabling Machine Identity Isolation is the temporary domain workaround, according to BleepingComputer on September 17, 2026.
- Switching affected audio hardware to 2-channel mode can restore sound in some cases, according to BleepingComputer on September 14, 2026.
- AMD Radeon crashes and some Explorer failures remain unresolved or unconfirmed, according to TechSpot on September 15, 2026.
Why can valid domain credentials still fail?
No permanent domain-login fix has shipped, BleepingComputer reported on September 17, 2026.
The Windows 11 bug can occur after KB5124008 on Windows 11 24H2 or 25H2, or KB5124012 on Windows 11 26H1, according to BleepingComputer on September 17, 2026. Microsoft confirmed that the updates begin honoring existing or policy-provisioned Machine Identity Isolation enforcement settings, BleepingComputer reported on September 17, 2026.
Machine Identity Isolation is supported only with domain controllers running at a Windows Server 2025 Domain Functional Level or above, according to BetaNews on September 17, 2026. Affected machines can lose their secure channel to an on-premises Active Directory domain, reject valid interactive credentials and display a failed trust-relationship message, while cached offline sign-in may continue working, BetaNews reported on September 17, 2026.
Microsoft's temporary instruction is to disable Machine Identity Isolation through the same management method that enabled it, according to BleepingComputer on September 17, 2026. The cost is administrative work and risk: BleepingComputer warned on September 17, 2026 that enabling enforcement and then disabling it can require the device to be unjoined and rejoined to the domain.
Is the USB audio failure fully fixed?
USB Audio Class 1.0 start failures remain unfixed, PCWorld reported on September 14, 2026.
KB5124008 affects Windows 11 24H2 and 25H2, while KB5124012 affects Windows 11 26H1, and PCWorld reported on September 14, 2026 that some USB Audio Class 1.0 devices may fail to start or produce sound. BleepingComputer reported on September 14, 2026 that affected machines can show Code 10 in Device Manager, no audio output, and unresponsive volume controls and sound settings.
Some devices work in standard stereo but fail with multichannel features, including 3D audio or 8-channel modes, according to PCWorld on September 14, 2026. ZDNET reported on September 14, 2026 that switching the device to Stereo can temporarily restore sound, although the workaround costs the affected person multichannel output.
KB5129195 repairs 8-channel and 3D modes on some devices that already worked in stereo, but TechSpot reported on September 15, 2026 that devices which fail to start, produce no sound or leave volume at zero remain broken. I would not treat Stereo as a universal repair because PCWorld reported on September 14, 2026 that no known workaround existed for the complete start failure.
Which reported failures remain uncertain?
AMD Radeon crashes remain unresolved, TechSpot reported on September 15, 2026.
TechSpot reported on September 15, 2026 that users described driver timeouts, black screens, dropped displays and complete system freezes after the September update, across hardware ranging from the RX 6600 through the RX 7000 series to the RX 9070 XT. Not every Radeon machine is affected, and TechSpot said on September 15, 2026 that some users restored stability by uninstalling the September update.
I would not present uninstalling the update as a confirmed repair because TechSpot characterized the Radeon evidence as user reports on September 15, 2026, not a Microsoft-confirmed resolution. Removing the September update also removes the update whose regressions KB5129195 was designed to repair, according to TechSpot's account of the update sequence on September 15, 2026.
For anyone triaging a Windows KB update problem, status matters more than volume of complaints. TechSpot reported on September 15, 2026 that AMD Radeon crashes and Explorer failing to load remained among the disruptive unresolved complaints, while some other reported problems were still officially unconfirmed.
What can a person do today?
Install KB5129195 where offered, then apply targeted workarounds to unresolved failures, TechSpot reported on September 15, 2026.
For Remote Desktop or Host Compute Service trouble on Windows 11 24H2 or 25H2, I would install KB5129195 because TechSpot reported on September 15, 2026 that the emergency update repairs those regressions. My September 15 report on KB5129195 provides the earlier checkpoint for those repairs.
For a failed domain trust relationship after KB5124008 or KB5124012, I would first try cached offline credentials where available, because BetaNews reported on September 17, 2026 that offline sign-in may continue working. An administrator can then disable Machine Identity Isolation through the method that enabled it, but BleepingComputer warned on September 17, 2026 that an incorrect enable-and-disable sequence may require leaving and rejoining the domain.
For USB audio that still works in stereo, I would switch from 3D audio or 8-channel mode to 2-channel mode, because BleepingComputer reported on September 14, 2026 that affected users restored sound that way. For Code 10, no sound or a device that will not start, I would test another connection or device rather than claim a software fix, because TechSpot reported on September 15, 2026 that KB5129195 leaves those failures unresolved.