[Bug]: Some folders/files not getting synced

[B5JohnSheridan]

⚠️ Before submitting, please verify the following: ⚠️

• This is a bug, not a question or a configuration issue.
• This issue is not already reported on Github (I've searched it).
• Nextcloud Server and Desktop Client are up to date. See Server Maintenance and Release Schedule and Desktop Releases for supported versions.
• I agree to follow Nextcloud's Code of Conduct

Bug description

We are using several group folders and in some of them we experience something very strange: Modified or new files and folders are not appearing in the VFS of windows clients. The new folders can however be seen in the settings dialog of the nextcloud client!
In the Screenshot, the "Testordner" can be seen in the Tree view of the settings dialog but not in the VFS on disk.
A forced sync does not help, also a restart of the client or the PC does not help either. The only things that are helping are removing the folder sync and adding it again or stopping the client, removing the sync*.db and restarting the client. This however does not help for the future, at least after a while or even right away, new files/folders are again not synced.
The opposite direction works: Modified files or new folders are synced to the server.

Tree view shows "Michaels Testordner" and "Testordner":

However, in the VFS those folders are not appearing

We tried to create a new group folder and move all from the affected group folder in the new one. Strange enough, this did not help on some clients.
Most of our group folders do not show this problem.

I grepped through through the log files but since there is not a clear moment in time where the problem happens, I could not find anything meaningful. There have been multiple warnings like those:

2023-11-25 19:08:30:309 [ warning nextcloud.sync.networkjob.put.multi C:\Users\User\AppData\Local\Temp\windows-18408\client-building\desktop\src\libsync\putmultifilejob.cpp:94 ]:      oneDevice has error: "Unbekannter Fehler"
2023-11-25 19:08:30:309 [ warning nextcloud.sync.propagator.bulkupload C:\Users\User\AppData\Local\Temp\windows-18408\client-building\desktop\src\libsync\bulkpropagatorjob.cpp:410 ]:  Server does not support X-OC-MTime ""
2023-11-25 19:08:30:810 [ warning default qrc:/qml/src/gui/tray/SyncStatus.qml:68 ]:    qrc:/qml/src/gui/tray/SyncStatus.qml:68:30: QML ProgressBar: Binding loop detected for property "palette.window"
2023-11-25 19:07:46:054 [ warning nextcloud.sync.networkjob C:\Users\User\AppData\Local\Temp\windows-18408\client-building\desktop\src\libsync\abstractnetworkjob.cpp:221 ]:    QNetworkReply::ContentNotFoundError "Server hat \"404 Not Found\" auf \"GET https://server/index.php/core/preview?fileId=00139420oc9s5bkwvcge&x=2560&y=2560\" geantwortet" QVariant(int, 404)
2023-11-25 19:07:46:055 [ warning nextcloud.sync.credentials.webflow C:\Users\User\AppData\Local\Temp\windows-18408\client-building\desktop\src\gui\creds\webflowcredentials.cpp:208 ]: QNetworkReply::ContentNotFoundError
2023-11-25 19:07:46:055 [ warning nextcloud.sync.credentials.webflow C:\Users\User\AppData\Local\Temp\windows-18408\client-building\desktop\src\gui\creds\webflowcredentials.cpp:209 ]: "Error transferring https://server/index.php/core/preview?fileId=00139420oc9s5bkwvcge&x=2560&y=2560 - server replied: Not Found"

Steps to reproduce

• Create a file or folder on the server in the affected group folder.
• Check in the VFS of the client for the file/folder (not there)
• Check in the settings dialog of the Nextcloud Client for the folder (it is there)
• Force sync and check again in the VFS (not there)
• Stop client, erase sync*.db file, restart client
• After sync, file/folder is in VFS, however newly added files/folders afterwards are also not getting added again

Expected behavior

Obviously, new/modified files and new folders should appear in the VFS, at least after a forced sync.

Which files are affected by this bug

Testordner

Operating system

Windows

Which version of the operating system you are running.

Windows 10

Package

Appimage

Nextcloud Server version

27.1.4

Nextcloud Desktop Client version

3.10.1

Is this bug present after an update or on a fresh install?

Fresh desktop client install

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

Are you using an external user-backend?

• Default internal user-backend
• LDAP/ Active Directory
• SSO - SAML
• Other

Nextcloud Server logs

No lines generated in /settings/admin/logging for this issue

Additional info

No response

[B5JohnSheridan]

We narrowed this down to be this groupfolder issue regarding nested groupfolders and the desktop client. Strange enough, it does not affect all users and all nested groupfolders in the same amount. Some folders are not working for certain users at all, e.g. no changes ever sync, while in other folders and for other users, everything works as expected. We used a circumvention based on the "7." in the above ticket for the time being.