[Bug]: Nextcloud Desktop on Windows deletes files on a massive scale randomly with no user interaction

[GAPPSRefusenik]

⚠️ 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've searched 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

Nextcloud Desktop just deleted about 300GB of my data without any user interaction. This happened twice at the end of last year when I was running outdated hardware and software. After New Year's, I did a complete fresh install of Nextcloud AIO on much more capable hardware (bare metal), and also got a new desktop machine with a fresh install of Windows 10. Everything went smooth for weeks, then suddenly I noticed the free space on my system drive.

Fortunately, I make daily back ups, and I could restore most files from the trash bin. Still, having to restore such a massive amount of files is always a tough blow. This should definitely not happen on a production machine.

When it happened last year, I thought the reason might have been due to a bug in how Windows virtual file support works, because prior to this incident, I only ever had files deleted randomly by my Surface Pro device where I have virtual files enabled on the desktop client. So after the second mass deletion within a week last year, I simply 'pulled the plug' and uninstalled the desktop client from my Surface Pro device.

I have never had virtual files enabled on my desktop though, so I guess this can be ruled out now. It's really a complete puzzle to me why this keeps happening. The attached 'permanent_delete' log files from the desktop client that I pulled out of the AppData directory only shows the 'delete' command next to the folders it wiped clean. At least that's all I can take away from them.

Strangely enough, out of the three very basic folders I have in my sync chain, 'Documents', 'Pictures' and 'Videos', the random auto-deletion only ever cleans out my picture and video files. All that remained after each of these three incidents were empty folders and sub-folders. My document files however apparently remained untouched.

Perhaps the devs can figure it out somehow. Of course I've done a bunch of research, and I'm not the only one who has experienced this issue. The others seem to be as clueless as I am from the posts I've read. The only hint I ever got was someone mentioning something about 'special environments' like a TrueCrypt container. In the interest of full disclosure, I do want to mention that the system drives of my desktop and Surface device are both fully encrypted by VeraCrypt, as is the drive hosting the sync data on the Nextcloud server, configured as external storage. Not sure if this might have anything to do with anything, but I did notice that applications had trouble detecting my encrypted drives in the past. That's the reason I could never use Veeam for backups of my Nextcloud data. It simply couldn't read the encrypted drive.

nextcloud_desktop_permanent_delete_logs.zip

Steps to reproduce

I just have to wait and suddenly realize that all my precious data is gone without any user interaction.

Expected behavior

Nextcloud only deletes files initiated by the user, not randomly on its own accord.

Which files are affected by this bug

Everything in the log files since it was all deleted.

Operating system

Windows

Which version of the operating system you are running.

Windows 10 IoT Enterprise LTSC 2021

Package

Official Windows MSI

Nextcloud Server version

30.0.4

Nextcloud Desktop Client version

3.15.3

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

Updated from a minor version (ex. 3.4.2 to 3.4.4)

Are you using the Nextcloud Server Encryption module?

Encryption is Disabled

Are you using an external user-backend?

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

Nextcloud Server logs

Additional info

External storage via SMB is configured for each Nextcloud user with the "/" folder mounted, making Nextcloud automatically display and write all user data to the external storage drive. Quite a nifty workaround I must say.