Microsoft has pushed another Canary‑channel preview for Windows 11 — build 27943 — that stitches up a cluster of user‑visible annoyances while leaving two serious deployment blockers on the books. The flight addresses a persistent Settings > System > Storage > Temporary files scanning hang, squashes several taskbar and HDR glitches, and removes a noisy Pluton‑related Event Viewer entry that had been alarming administrators. At the same time, Insiders should be cautious: a rollback during installation (0xC1900101‑style) and an Arm64 kernel bugcheck regression remain active known issues that can force a recovery or repeated retries. Early community reports, third‑party coverage, and Insider threads document the changes and the outstanding risks, making this build a mixed bag for testers and developers. (blogs.windows.com)
Canary‑channel builds are intentionally experimental: they are the earliest platform flights and frequently combine small quality fixes with experiments that may never ship. That design makes them valuable for spotting regressions early, but also inherently unstable for daily‑driver machines. Microsoft’s own Canary posts and the community’s build trackers show a steady cadence of maintenance updates in late summer and early fall — builds in the 27xxx range have focused on reliability housekeeping and surface‑level bug fixes rather than major feature rollouts. (blogs.windows.com)
Build 27943 continues that pattern: it’s primarily a polish release that targets several longstanding pain points, especially the temporary files scanner and a nuisance event log entry associated with development code paths for the Microsoft Pluton cryptographic provider. The build also includes a handful of display and taskbar repairs that will be felt by everyday users, and a group of known problems aimed squarely at testers and developers — notably, PIX playback incompatibilities and a hardware‑specific Arm64 green‑screen regression. Community threads and Insiders’ summaries provide the most complete picture of what changed and what remains broken.
For Insiders and testers the recommendation is straightforward: evaluate the fixes you need on test hardware, follow the Device Manager audio workaround if you see the yellow exclamation marks, and do not deploy this build on primary devices until Microsoft marks the high‑impact known issues as resolved. Developers dependent on PIX should pause upgrades until PIX compatibility is restored, or seek private PIX builds via official channels. Backups, recovery media, and a conservative rollout strategy remain essential when engaging with Canary‑channel builds.
The Windows Insider and community threads remain the best near‑real‑time place to track the status of these fixes and the outstanding regressions. File a clear, well‑documented report through Feedback Hub if you reproduce a regression and attach diagnostic logs — high‑quality feedback accelerates triage and the arrival of fixes in subsequent flights.
Source: Neowin Microsoft fixes stuck temporary file cleaning and other bugs in Windows 11 build 27943
Canary‑channel builds are intentionally experimental: they are the earliest platform flights and frequently combine small quality fixes with experiments that may never ship. That design makes them valuable for spotting regressions early, but also inherently unstable for daily‑driver machines. Microsoft’s own Canary posts and the community’s build trackers show a steady cadence of maintenance updates in late summer and early fall — builds in the 27xxx range have focused on reliability housekeeping and surface‑level bug fixes rather than major feature rollouts. (blogs.windows.com)Build 27943 continues that pattern: it’s primarily a polish release that targets several longstanding pain points, especially the temporary files scanner and a nuisance event log entry associated with development code paths for the Microsoft Pluton cryptographic provider. The build also includes a handful of display and taskbar repairs that will be felt by everyday users, and a group of known problems aimed squarely at testers and developers — notably, PIX playback incompatibilities and a hardware‑specific Arm64 green‑screen regression. Community threads and Insiders’ summaries provide the most complete picture of what changed and what remains broken.
What’s fixed in Build 27943
The public changelog for this Canary flight breaks the work into a few short categories. The practical impact of each fix ranges from mere annoyance relief to genuine operational improvements.General fixes
- Fixed a hang in Settings > System > Storage > Temporary files: The scan could stall while enumerating temporary content and previous Windows installations; that hang has been fixed so the Settings UI can finish scanning and present the cleanup options as expected. This addresses a confusing user scenario where Storage reported stale or missing entries and prevented cleanup of remaining Windows installations. (blogs.windows.com)
- Miscellaneous stability & UX cleanups: a collection of small corrections improve the overall experience for Insiders on the build, consistent with a maintenance flight rather than feature work.
Taskbar
- Resolved a duplicate thumbnail preview when hovering over minimized apps after switching between virtual desktops. This fixes a visual duplication that could confuse users who rely on taskbar thumbnails for window navigation. The change reduces a glaring UI oddity in multi‑desktop workflows.
Display and graphics
- Addressed a regression where HDR could immediately turn off after being enabled in Settings. The fix restores expected HDR behavior when users toggle the feature on, preventing an instant fallback that left displays in SDR. For users who depend on accurate color and HDR workflows this reduces interruptions and the need for manual toggling.
Other notable fixes
- Cleared noisy Event Viewer entries tied to the Microsoft Pluton Cryptographic Provider that were being logged with error ID 57 on some machines after boot. Microsoft’s triage has previously classified these CertEnroll/Pluton entries as cosmetic in many cases, and the build removes that spurious noise so administrators aren’t chasing false alarms. (borncity.com)
- Fixed a Quick Settings PIN confirmation regression: if you needed to enter a PIN to cast from Quick Settings, pressing Enter didn’t confirm the PIN — the build restores Enter as an acceptance input so casting flows are smoother.
- Made another pass on Group Policy Editor rendering with Chinese display language to remove unexpected blank areas and improve layout fidelity for administrators using that locale. This is an important regional polish for enterprise management tools.
Known issues and blockers you must weigh
Despite the quality work above, Microsoft flagged several significant known issues for this (and closely adjacent) Canary flights. These are not theoretical: multiple install attempts, forum reports, and Microsoft’s own notices indicate real risk.- Installation rollback: Some Insiders experience a rollback during installation with either an 0xC1900101‑0x20017 or 0xC1900101‑0x30017 error. Retrying the update often yields another rollback. Microsoft is working on a fix; however, this is a hard blocker for affected devices because it prevents the update from sticking. Backups and recovery plans are essential before attempting this build. (elevenforum.com)
- Arm64 kernel bugchecks: A new, Arm64‑specific issue is under investigation where some Arm64 PCs see an increase in bugchecks (green screens) with the error IRQL_NOT_LESS_OR_EQUAL. If you run Windows on Arm hardware, treat this build as high risk until Microsoft issues a targeted fix.
- PIX playback for developers: PIX on Windows may be unable to play back GPU captures on this OS version; Microsoft expects a PIX release to resolve playback compatibility, with early estimates pointing to a late‑September update. Developers who rely on PIX for GPU capture analysis should delay upgrading or use the PIX “Send Feedback” path / DirectX Discord to request private builds. PIX’s capture/playback compatibility can break across OS and driver boundaries, and a PIX release will be required to reestablish the expected workflow. (blogs.windows.com)
- Graphics flicker and browser rendering: Insiders have reported screen flickers when using browsers (and possibly other scenarios) on affected builds. Microsoft is investigating; the issue likely sits at the hardware/driver/OS interaction layer and is another reason to treat the Canary channel as unsuitable for mission‑critical systems.
- Audio driver break: Some Insiders see audio stop working with Device Manager showing yellow exclamation marks on devices such as “ACPI Audio Compositor.” The build notes include a manual Device Manager workaround: update the faulty device driver by choosing “Browse my computer for drivers” → “Let me pick from a list of available drivers on my computer” and selecting the most recent dated driver from the list. If the device shows a list of common hardware types instead of a specific driver, that device is not related to this known issue. Repeat the steps for each affected device.
Why these fixes matter (and why some regressions are dangerous)
Storage scanning hang — more than an annoyance
The Temporary files scanner lives in Settings and is users’ path to reclaiming space without invoking legacy tools. When the scanner freezes or silently omits previous Windows installations (Windows.old), two things happen:- Users are left with inaccurate storage telemetry, which can cause confusion and poor decisions (e.g., not freeing space when needed).
- Automated cleanup and recovery workflows that rely on accurate Storage readings can break, complicating both home‑user maintenance and enterprise imaging/maintenance tasks.
Event Viewer Pluton noise — operational impact
The CertEnroll Event ID 57 entries referencing the Microsoft Pluton Cryptographic Provider were a classic false positive case: error‑level logs that do not reflect operational breakage, but which trigger alerts in centralized monitoring systems. Administrators saw repeated Error entries on boot, which can generate alert fatigue or, worse, automated remediation workflows unnecessary for a cosmetic artifact. Removing that noise helps incident response teams focus on real issues and reduces the operational overhead of chasing phantom errors. Multiple independent writeups and Microsoft’s own guidance previously characterized these messages as benign; this build’s fix removes the nuisance. (borncity.com)PIX playback and developer workflows
For graphics developers and studios, PIX is a primary capture & analysis tool for Direct3D workloads. When PIX cannot play back GPU captures because the OS or drivers changed, debugging grinds to a halt. Microsoft’s plan to release a PIX update to restore replay functionality is sensible, but the break highlights how tightly GPU tooling couples to OS and driver versions. Teams that depend on precise GPU capture analysis should hold off on Canary upgrades until PIX compatibility is confirmed. (blogs.windows.com)Arm64 bugchecks and rollback risk — production impact
Two issues stand out as showstoppers for production use:- Rollback during installation: this prevents the update from applying cleanly and can leave machines in repeated upgrade attempts or force recovery operations.
- Arm64 IRQL_NOT_LESS_OR_EQUAL bugchecks: unrecoverable kernel errors on Arm hardware can cause data loss, crash loops, or hardware bricking in the worst cases.
Practical guidance: who should (and shouldn’t) install Build 27943
- Recommended for:
- Windows enthusiasts and testers with spare devices who actively file feedback.
- Developers who need to confirm bug behavior on pre‑release OSes, provided they don’t rely on PIX playback until the PIX update ships.
- IT professionals validating specific fixes (for example, Storage scanning or CertEnroll noise) in controlled lab environments.
- Not recommended for:
- Production laptops or desktops where uptime and recovery are critical.
- Arm64 devices used as daily drivers until the IRQL‑related bugcheck is resolved.
- Systems that cannot tolerate the risk of an installation rollback or audio/device driver regressions.
- Create a full system image or a complete backup before upgrading.
- Build a USB recovery drive and ensure you have install media to fall back to if the device becomes unusable.
- Defer the update on business machines and wait for Microsoft to mark the issue resolved in Flight Hub or a subsequent Canary build.
- If you are an enterprise admin, test the build across a representative hardware fleet and monitor application and driver compatibility closely.
Troubleshooting tips and temporary workarounds
Below are practical steps pulled from the build notes and community guidance for the most common problems reported on adjacent Canary flights.- If you encounter the audio yellow exclamation mark:
- Open Device Manager.
- Right‑click the device with the yellow exclamation mark and select Update driver.
- Choose Browse my computer for drivers.
- Select Let me pick from a list of available drivers on my computer.
- Choose the driver entry with the most recent date and click Next.
- Repeat for each device exhibiting the exclamation mark. This is the workaround Microsoft outlined for affected Insiders.
- If the build fails to install with 0xC1900101 rollback:
- Don’t repeatedly retry in a loop. Create a recovery image, then:
- Boot to recovery media and attempt repair.
- If the device continues to roll back, wait for the next flight that contains a specific fix (Microsoft is tracking this as a known issue).
- For business fleets, defer the update via Windows Update for Business policies until the issue is resolved.
- If you rely on PIX:
- Defer upgrading until PIX announces a compatibility release. If you must upgrade, contact the PIX team via the “Send Feedback” button in PIX or the DirectX Discord to request a private build that restores playback. Microsoft estimated a PIX release by the end of September to address playback incompatibility on recent Insider builds. (blogs.windows.com)
Developer and enterprise considerations
- Testing matrix: Hardware diversity matters. Canary regressions tend to surface on specific combinations of chipset, GPU vendor, and driver versions. Enterprise test teams should prioritize the following permutations:
- Intel/AMD/NVIDIA discrete and integrated GPU drivers
- Arm64 vs x64 device classes
- Latest OEM driver stacks versus Microsoft‑provided drivers
- Telemetry and logging: The CertEnroll/Pluton scenario is a reminder to tune alerting thresholds in centralized logging systems. Cosmetic error‑level logs can cause unnecessary escalations. Correlate Event IDs with known issue lists before opening high‑priority incidents. (windowsforum.com)
- Change control: For fleets managed with WSUS, Intune, or Windows Update for Business, maintain a conservative deployment ring and gate Canary or Beta candidates until fixes propagate into broader channels or Microsoft marks the issue as resolved in Flight Hub. Canary builds are for early feedback, not wide enterprise adoption.
Critical assessment — strengths and risks
Notable strengths
- The build corrects several user‑facing quality issues that previously degraded day‑to‑day usability: the temporary files scanner hang and the Pluton Event Viewer noise were both high‑annoyance problems with measurable operational impact, and their resolution improves the platform’s manageability.
- Microsoft is continuing an incremental, pragmatic approach to Settings migration and UI parity while triaging plumbing bugs — the Canary channel remains useful for catching regressions early in the development pipeline. That iterative approach helps isolate wide‑impact regressions before they reach broader channels. (blogs.windows.com)
Key risks and downsides
- Canary volatility remains the largest single risk: installation rollbacks and platform‑level driver/compatibility regressions (PIX, Arm64 bugchecks, screen flicker) can impede testing and are likely to raise help‑desk traffic if deployed broadly. These are not cosmetic; they affect recovery and operational stability.
- Developer toolchain fragility: PIX incompatibilities illustrate how quickly OS updates can impair developer workflows. For game or graphics developers, even short interruptions to capture/playback functionality can significantly slow debugging and release timelines. (devblogs.microsoft.com)
- Communication gap: At the time community reports circulated, Microsoft’s central blog posts sometimes lag coverage on secondary sites or community threads, leaving Insiders reliant on third‑party writeups for details. That makes it harder to correlate observed behavior with official guidance; administrators should consult Flight Hub and Microsoft’s support documentation for authoritative status. Where official blog entries exist for nearby builds (for example, Build 27934), they can clarify the broader roadmap — but for some Canary flights the public notice may be sparse or delayed. (blogs.windows.com)
Bottom line
Windows 11 build 27943 is a focused maintenance flight that resolves several high‑visibility annoyances — most notably the temporary files scanning hang and the Pluton/Cer tEnroll Event Viewer noise — and patches a handful of visual and UX glitches. Those changes are meaningful for daily user experience and for administrators who were seeing spurious log alerts. However, the build is not a safe upgrade for everyone: installation rollbacks, an Arm64 kernel regression, PIX playback incompatibility, graphics flicker, and an audio driver issue all remain live concerns that make this unsuitable for production machines and critical systems.For Insiders and testers the recommendation is straightforward: evaluate the fixes you need on test hardware, follow the Device Manager audio workaround if you see the yellow exclamation marks, and do not deploy this build on primary devices until Microsoft marks the high‑impact known issues as resolved. Developers dependent on PIX should pause upgrades until PIX compatibility is restored, or seek private PIX builds via official channels. Backups, recovery media, and a conservative rollout strategy remain essential when engaging with Canary‑channel builds.
The Windows Insider and community threads remain the best near‑real‑time place to track the status of these fixes and the outstanding regressions. File a clear, well‑documented report through Feedback Hub if you reproduce a regression and attach diagnostic logs — high‑quality feedback accelerates triage and the arrival of fixes in subsequent flights.
Source: Neowin Microsoft fixes stuck temporary file cleaning and other bugs in Windows 11 build 27943