[Windows Incompatibility?] Desktop folder sync issue after Windows Sec Update

[TheHerjei]

This is NOT a bug by Nextcloud Client, but (i think) an incompatibility with latest Windows Security Updates.

Configurations:
Client Machines: Windows 11 25H2 Home edition
Nextcloud Client Version: 33.0.2.20260331
Nextcloud Client configured with a single folder sync in Virtual Files mode with the default path C:\Users\USERNAME\Nextcloud

Windows user configured with Desktop folder redirected to C:\Users\USERNAME\Nextcloud\Desktop
And "Keep on this device" option activated on Desktop folder.

The issue:
After April 2026 MS Tuesday Patch, (KB5083769, KB5082417 and KB5079473), after machine reboot, explorer.exe just doesn't work as expected while Nextcloud Client is running.

User cannot open File Explorer and cannot open Settings page, they just won't opens. Nextcloud client process run in backround and tray icon appear, but it won't open either the "sync panel" or settings or context menu.

Windows context menu won't open too.

When user open task manager (with ctrl+alt+canc or by right-clicking on icon bar) and kill nextcloud.exe process, suddenly File Explorer and context menus return to work as expected.

But Nextcloud folder remain inaccessible due to sync client closed improperly and Desktop folder (inside Nextcloud one) will give security alert and cannot be opened.

What I've done to recover:

• Kill Nextcloud process
• Remove Nextcloud client configuration file in C:\Users\USERNAME\AppData\Roaming\Nextcloud\nextcloud.cfg
• Rename C:\User\USERNAME\Nextcloud to something else like "Nextcloud_OLD"
• Logout/Login windows user
• Reconfigure Nextcloud client

[mgallien]

@TheHerjei I cannot reproduce with a similar Windows machine that is also up to date
can you send us some logs ?
they are critical to understand what happen