Sync error loop on Windows 10, after reinstalling app crashed during sync and starts to delete files after automatic restart

Expected behaviour

File sync using virtual files on Windows 10 after automatic app upgrade.

Actual behaviour

A group of regular PDF files are ignored in the sync process due to an unknown reason and displayed in the ignore window of the desktop client. Client keeps trying to resync the same group of files though produces the same error, hence get caught in a loop and never completes the sync for which other files pending syncing are put on hold and never uploaded/downloaded. After reinstalling the app, on some computers the app crashes and automatically restarts or is manually restarted. After restart the app starts to remove all files from the server that have not yet been downloaded, rather than picking up the sync where it left off and downloading those files.

Steps to reproduce

  1. Automatic upgrade to latest version of Windows 10 OwnCloud client without changing or reinstalling sync account.
  2. Wait for sync loop error.
  3. Reinstall app by downloading latest version from
  4. Reconfigure sync account and link an empty folder where the files should download.
  5. Files start to download, then wait for crash.
  6. After automatic or manual app restart, files are being removed from server rather than being downloaded.

Server configuration

Operating system: CentOS 7.8
Web server: Apache/2.4.6 (CentOS)
Database: mysql Ver 15.1 Distrib 5.5.65-MariaDB
PHP version: PHP 7.2.33
ownCloud version: ownCloud 10.5.0
Storage backend (external storage): No external storage

Client configuration

Client version: and
Operating system: Windows 10 Home 2004 19041.685
OS language: Spanish
Installation path of client: C:\Program Files (x86)\ownCloud\


No error log file was configured on either of the 12 machines with the same issue. In order to avoid getting more files deleted (we already have to manually restore over 230,000 files from different user trash bins) we can’t run the app again to reproduce the error as it sometimes takes several hours for the app to crash and then in a few minutes starts to remove thousands of files. We do have the server log file, activity output in client window as well as the .owncloudsync.log file in the OwnCloud file folder window in 2 of the machines.

Seen you opened issue on GH. Let’s continue there…