[Bug]: NextCloud Client 33.0.x (up to 33.0.5) problem with Sync and explorer

[Eagle46-ita]

⚠️ This issue respects the following points: ⚠️

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

Bug description

Hello,
while using client version 33.0.X, we have encountered several issues related to synchronization and Windows 11 File Explorer freezing.
After installation, the client initially works without any issues. However, during synchronization, it randomly goes offline and loses connection, preventing proper synchronization of files uploaded to the cloud.
Additionally, when attempting to browse files through Windows 11 File Explorer, the system freezes completely, and it is necessary to restart File Explorer to restore normal functionality.
We have tested all versions of the 33.0.X client with both a 1 TB cloud and a 30 TB cloud, and the same issues occur in both scenarios.

Steps to reproduce

1.Install client version 33.0.X on a Windows 11 machine.
2.Complete the initial setup and start file synchronization.
3.Allow the client to run and sync data with the cloud.
4.After some time (random behavior), observe the client status.
5.Try to browse synchronized files using Windows 11 File Explorer.

Expected behavior

The client should remain online and connected.
Files should synchronize correctly with the cloud.
File Explorer should remain responsive while browsing files.

Nextcloud Server version

33

Operating system

Debian/Ubuntu

PHP engine version

PHP 8.3

Web server

Apache (supported)

Database engine version

MariaDB

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

Fresh Nextcloud Server install

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

What user-backends are you using?

• Default user-backend (database)
• LDAP/ Active Directory
• SSO - SAML
• Other

Configuration report

{
    "system": {
        "passwordsalt": "***REMOVED SENSITIVE VALUE***",
        "secret": "***REMOVED SENSITIVE VALUE***",
        "trusted_domains": [
            "ws.gruppoebano.com"
        ],
        "datadirectory": "***REMOVED SENSITIVE VALUE***",
        "dbtype": "mysql",
        "version": "33.0.2.2",
        "overwrite.cli.url": "http:\/\/ws.gruppoebano.com",
        "dbname": "***REMOVED SENSITIVE VALUE***",
        "dbhost": "***REMOVED SENSITIVE VALUE***",
        "dbtableprefix": "oc_",
        "mysql.utf8mb4": true,
        "dbuser": "***REMOVED SENSITIVE VALUE***",
        "dbpassword": "***REMOVED SENSITIVE VALUE***",
        "instanceid": "***REMOVED SENSITIVE VALUE***",
        "installed": true,
        "maintenance": false,
        "maintenance_window_start": 1,
        "check_data_directory_permissions": false,
        "serverid": 0,
        "default_phone_region": "IT",
        "memcache.local": "\\OC\\Memcache\\APCu",
        "memcache.distributed": "\\OC\\Memcache\\Redis",
        "memcache.locking": "\\OC\\Memcache\\Redis",
        "redis": {
            "host": "***REMOVED SENSITIVE VALUE***",
            "port": 6379
        }
    }
}

List of activated Apps

Nextcloud Signing status

Nextcloud Logs

Additional info

No response

[mateuszzadorski]

Experiencing similar issues on Win11, docker deployment on long running instance.

[ACAPax]

I'm also having similar issues with a large NextCloud folder on Windows 11 using VFS.
I tested every version of the NextCloud 33.0.x client for several days and then downgraded back to version 4.0.8 each time, which immediately resolved the issues every time.

[Eagle46-ita]

Hello,
I performed a network analysis using Wireshark to investigate the anomalous behavior of client version 33.0.5. The issue can be reproduced with the following steps:

1-Clean installation of the client
2-Configuration of the client to connect to the server
3-Synchronization completes successfully
4-Folders and files are accessible initially
5-The Nextcloud client goes offline automatically
6-Access to files becomes blocked

Additionally, I noticed that the client suggests installing version 33.0.3, even though I am already using the latest released version.
Attached is the Wireshark report, which highlights the points where the client stops communicating. I hope this information can help with the investigation.

nextcloud.pcapng.gz

Client version: 33.0.5
Windows 11 build: 26200.8655

[Eagle46-ita]

Update
I am currently testing version 34.0.0 RC1 of the Nextcloud Windows desktop client.
Environment:

Client: 34.0.0 RC1
Sync mode: Virtual Files (VFS)
Nextcloud Server: 33.0.2
File sharing setup: Team folders + External storage

After one full day of use, I have not encountered the issues previously reported.
The only situation worth mentioning occurred when I added a large external storage folder (~400 GB). At that moment, the account temporarily went offline for about 30 seconds, but then it automatically came back online.
Importantly, after reconnecting, the client did not start a full re-synchronization, which suggests normal recovery behavior.
At the moment, everything appears to be stable.
I will continue testing the client and will provide further updates if anything changes.

[Eagle46-ita]

New update

Debug.zip

I installed the 34.0.0 client on another computer, and unfortunately the issue described in this topic occurred again. The client starts the synchronization, but after a while it freezes, goes offline, and when it comes back online it restarts the synchronization from the beginning.
I have created a debug archive from the application and I am attaching it here. I hope this information will be helpful in identifying the problem.
Thank you.

[ACAPax]

I also took a look at your logs and compared them to mine. Unfortunately, it seems our problems are different after all. Your logs actually show that the syncs were unsuccessful. Mine always show “successful.”
So if these are related errors after all, it’s probably because your folder is much larger than mine. The times listed for the syncruns in your log are 3 to 5 times longer than mine. If it is the same error, though, it’s possible that you’re also experiencing a timeout.