two-way sync is repeatedly downloading files over and over #17923

⚠️ Before posting ⚠️

• This is a bug, not a question or an enhancement.
• I've searched for similar issues and didn't find a duplicate.
• I've written a clear and descriptive title for this issue, not just "Bug" or "Crash".
• I agree to follow Nextcloud's Code of Conduct.

Steps to reproduce

1. Enable two-way sync.
2. Watch it download folder contents.
3. After all contents are downloaded, it re-downloads everything again.

Expected behaviour

The files are downloaded once, then only changed files are downloaded.

Actual behaviour

Files are repeatedly downloaded again and again.

Android version

Android 17

Device brand and model

Samsung Galaxy S25 Ultra

Stock or custom OS?

Stock

Nextcloud android app version

35.0.2

Nextcloud server version

34.0.5

Using a reverse proxy?

Yes

Android logs

No response

Server error logs

{"reqId":"edMF7hm1iGTuR5oYhDKT","level":3,"time":"2026-10-30T08:47:20+00:00","remoteAddr":"112.213.140.215","user":"maddy","app":"no app in context","method":"PUT","url":"/remote.php/dav/uploads/maddy/13d4095abc27fb2022c7ed9f6d81f64a/000043","scriptName":"/remote.php","message":"Expected filesize of 104857600 bytes but read (from Nextcloud client) and wrote (to Nextcloud storage) 63381504 bytes. Could either be a network problem on the sending side or a problem writing to the storage on the server side.","userAgent":"Mozilla/5.0 (Android) Nextcloud-android/

Additional information

• Not running beta version. No client log was created.
• I believe the server logs are unrelated.