Microsoft shipped an optional preview cumulative update for Windows 11 23H2 in the Release Preview Channel that tackles a string of reliability bugs—from File Explorer showing only a single folder to SMB over QUIC timeouts and a dangerous ReFS hang. KB5064080 (build 22631.5840/22621.5840) also marks the general availability of Windows Backup for Organizations, a settings‑migration tool that IT can manage through Microsoft Intune.

Released as a “C” week non‑security quality preview, the package bundles Servicing Stack Update KB5064743 with the Latest Cumulative Update, which improves install reliability but demands careful rollback planning because SSUs are persistent. The update surfaced first in mid‑August as build 22631.5837 and was refined to 22631.5840 to address an update‑time glitch. Microsoft’s official support page and the Windows Insider blog detail the full fix list and installation guidance.

File Explorer Regressions Finally Quashed

For weeks, users reported that File Explorer sometimes opened to show only a single folder—often Desktop—rather than the expected Home view with recent files and recommended content. The behavior struck unpredictably, confusing users and generating helpdesk calls. Heavy SharePoint adopters who sync many document libraries into Explorer also suffered severe slowdowns when navigating folders or right‑clicking, with freezes that could last seconds.

KB5064080 delivers targeted fixes for both problems. While Microsoft does not publish exact code changes, the update corrects the conditions that caused Explorer to fall back to the useless single‑folder view and optimizes enumeration paths for cloud‑backed locations. In practice, the Home pane should now display full content, and the context‑menu and navigation lag when many SharePoint sites are mounted should vanish.

IT teams should test the fix on pilot devices that routinely mount several SharePoint sites. Validate by opening folders, right‑clicking in busy directories, and comparing response times before and after the update. If symptoms persist, third‑party file system filters or cloud storage connectors may still interfere, requiring vendor investigation.

SMB over QUIC Latency Mitigations

SMB over QUIC is Microsoft’s modern answer to VPN‑less file share access, using the QUIC transport over UDP for secure, low‑overhead connections—a key enabler for remote work and zero‑trust architectures. But administrators encountered intermittent delays and timeouts when accessing shares, causing slow file opens and stalled directory listings that frustrated users miles from the office.

The update includes mitigations that reduce those latency incidents, making SMB over QUIC more predictable. Testing should include file open operations and directory enumeration from remote networks, both pre‑ and post‑update. Pay special attention to environments with load balancers or firewalls that inspect QUIC traffic; intermediary devices can introduce symptoms that look like the OS‑level bug even after the fix is applied.

ReFS: Dodging a Server‑Halting Bullet

The Resilient File System underpins many enterprise virtualization and backup platforms. A rare but severe bug could cause a system hang when data deduplication and compression were both active on the same volume—an operational nightmare for storage‑intensive workloads. KB5064080 patches that race condition, preventing unexpected unresponsiveness during dedupe and compression jobs.

For shops running ReFS with both features turned on, testing in a lab cluster is non‑negotiable. Run deduplication cycles and heavy data ingestion while monitoring for hangs. Though the fix is welcome, always maintain robust backups before modifying storage stack parameters.

Windows Backup for Organizations: GA with Limits

The changelog highlights “New!” for Windows Backup for Organizations. This is not a full‑system backup tool; it captures and restores Windows settings, personalization, accessibility options, network profiles, and similar environment state when an Entra‑joined device is reprovisioned—ideally paired with Autopilot and modern deployment flows.

General availability means the feature is toggled on in the OS, but actual access is gated behind Intune configuration and Entra join status. IT admins must enable the restore setting in the Intune admin center and verify Conditional Access policies. A test backup‑and‑restore cycle on a non‑production device is essential before broad rollout. Do not mistake this for a replacement of full image or file backups; it is strictly a settings‑migration tool.

Other Fixes Worth Noting

KB5064080 also addresses a clutch of smaller but meaningful issues:

  • Copilot key reliability: Fixed a bug that could prevent the PC from restarting after using the Copilot hardware key.
  • Removable storage policy enforcement: A device management bug that let blocked USB devices operate is now resolved, strengthening data‑exfiltration controls.
  • IME and Unicode compliance: Extended Chinese glyphs and GB18030‑2022 requirements are now correctly rendered, critical for regulated and multilingual deployments.
  • Narrator accuracy: Incorrect screen reader announcements in Windows Hello settings are fixed, improving accessibility.
  • Wi‑Fi and Remote Desktop: Wi‑Fi reconnection after Group Policy changes and Remote Desktop camera enumeration both received stability patches.

Deployment Playbook

KB5064080 is opt‑in; it will not install automatically. Release Preview Insiders and IT pros can obtain it via Settings > Windows Update > Check for updates > Optional updates. Because the package combines an LCU with an SSU, uninstalling the SSU is not supported. To roll back, use DISM to remove only the LCU portion, but accept that the SSU remains.

Microsoft recommends a ringed rollout. A practical checklist:

  • Pilot on a diverse set of hardware: laptops, desktops, servers, and especially those with heavy ReFS usage.
  • Reproduce the File Explorer single‑folder issue and SharePoint‑mounted performance lags.
  • Test SMB over QUIC latency from remote locations.
  • Stress‑test ReFS with deduplication and compression simultaneously.
  • Validate Windows Backup for Organizations in a lab tenant with Intune, following Microsoft’s documentation.
  • Monitor event logs, community forums, and internal helpdesk for new regressions.

Risks and Considerations

As with any preview update, caution is warranted. Third‑party drivers, especially EDR/AV agents and file system filters, can clash with kernel‑level changes. Past cycles have surfaced edge‑case regressions on exotic hardware. The SSU’s persistence complicates rollback; a simple wusa uninstall of the MSU won’t work. Plan rollback carefully: keep golden images or system restore points ready.

Windows Backup for Organizations, while exciting, is not yet universally available across all tenants. Verify the feature appears in your Intune portal and that Conditional Access does not silently block it. Its scope is narrow—settings only—so retain existing backup infrastructure for applications and files.

Conclusion

KB5064080 is a pragmatic, operationally focused preview that silences many frustrating bugs. File Explorer reliability, SMB over QUIC performance, and ReFS stability directly affect daily productivity and server uptime. The addition of Windows Backup for Organizations, even with its tenant‑gated rollout, signals a maturing enterprise‑device‑management story from Microsoft. Organizations already grappling with these specific issues should evaluate the update in a pilot immediately. Everyone else benefits from a measured, ringed deployment toward a more stable Windows 11 23H2 environment.