[Bug]: [v34 RC5] Client crashes during discovery with WindowsError 57 (ERROR_INVALID_PARAMETER) in OCC::FileSystem::isFileLocked #10444

⚠️ 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 have searched for 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

This text was created with the use of AI - its an interpretation of the log that I shared with it after the problem discovery.

The Nextcloud Desktop Client (v34.0.0-RC5) repeatedly crashes during the initial/background sync discovery phase (ProcessDirectoryJob::NormalQuery). The sync process stalls and terminates after OCC::FileSystem::isFileLocked (filesystembase.cpp:735) continuously fails with WindowsError: 57: Falscher Parameter. (ERROR_INVALID_PARAMETER). This affects Windows Virtual Filesystem (VFS) setups when traversing deep folder structures, VFS placeholders, or extracted archive paths.

Steps to reproduce

1. Install Nextcloud Desktop Client v34.0.0 RC5 (or RC2) on Windows.
2. Enable Virtual Files (VFS / Cloud Files API).
3. Connect an account with large/deep directory trees or unpacked archive files (e.g., .tar structures with PaxHeader subdirectories).
4. Allow the client to run its initial or background discovery pass.

Expected behavior

The sync discovery phase should traverse local VFS placeholders without crashing or throwing invalid Win32 handle API parameter errors.

Which files are affected by this bug

Deeply nested directories and archive structures - I can share a log to a more secure upload environment

Operating system

Windows

Which version of the operating system you are running.

Windows 11

Installation method

Other

Nextcloud Server version

33.0.6

Nextcloud Desktop Client version

34 RC5

Did this occur after an update or on a clean installation?

Minor version update (i.e. 33.0.0 → 33.0.1)

Are you using the Nextcloud Server Encryption module?

No

Are you using an external user-backend?

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

Nextcloud Server logs

Additional info

No response