Client consistently stops syncing after a few minutes

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Describe the bug

The desktop client becomes stuck (stops syncing) after a few minutes syncing. Hitting "Restart sync" on the stuck share (or force sync on any other share) properly restarts the syncing process and syncs some more files, until it becomes stuck again. When stuck, it remains in that state seemingly forever (or at least for a whole day in my experience).

Expected behavior

The client should sync everything and not get stuck.

Steps to reproduce the issue

1. Drop files into a share
2. Wait for them to sync
3. Sync starts, but becomes stuck after a while

Screenshots

Logs

Here is what the client log shows several minutes after becoming stuck. It seems to complain about authenticating, but the UI still says the account is connected, and just restarting sync works, so I suppose this is not an auth issue. I don't see any obvious error either.

https://gist.github.com/gpothier/8dfb372643b83206b1c09a83729f9845

Client version number

ownCloud 6.0.1.17343 63ace8
Libraries Qt 6.8.3, OpenSSL 3.4.1 11 Feb 2025
Using virtual files plugin: suffix
OS: ubuntu-6.17.0-5-generic (build arch: x86_64, CPU arch: x86_64)
QPA: wayland

Desktop environment (Linux only)

Ubuntu 25.10, Gnome

Client package version and origin (Linux only)

Installed from https://download.owncloud.com/desktop/ownCloud/stable/latest/linux/Ubuntu_25.10

Installation path (Windows only)

No response

Server information

Infinite Scale 7.1.2 Community
ownCloud Web UI 11.3.1

On an on-prem k8s cluster in the same building as the client.

Additional context

I am migrating files from OwnCloud 10 to OCIS, so I moved quite a few files (about 30 GB in 10,000 files). I cannot identify any patter in the amount of files (or bytes) that are properly synced before it gets stuck

Start by reviewing the linked client log and reproducing the sync stall while migrating the reported 30 GB and 10,000 files. Trace the sync and authentication behavior around the point where syncing stops; done means the client completes the share synchronization without requiring a restart.