Folders disappear immediately after creation: "Conflict when uploading a folder. It's going to get cleared!"

Nextcloud version: 22.1.0
Operating system and version: Ubuntu 20.04
Client version: 3.3.5

The issue you are facing:
I have synced almost all my library (I have excluded some folders) with my Ubuntu laptop. I am using the experimental virtual filesystem for that, since I have maybe a couple TB of data and around 200000 files in nextcloud.

Most of my files are accessed via external storage using sftp connections. All of them have write permissions and I can check that by creating and deleting files from the web interface without any problems. Nextcloud check for changes in these external storages every 5 minutes. But the problem also affects native Nextcloud folders.

My problem comes from the ubuntu client. When I create a new folder, it immediately disappears, and in the client I can see the message: “Conflict when uploading a folder. It’s going to get cleared!”
Here’s a screenshot:

That happens when I create a new folder from the Nautilus browser, or even from the command line. If I create the folder in the web interface works just fine and gets synced, and same if I create the folder directly in the external storage outside nextcloud.

Yesterday it happened to me also with files, but it seems that now it lets me create files without problem.

I found almost no documentation for this problem on google. Does anyone have an idea what could be happening? I’m tring to see if Nextcloud is usable for my particular setup.

Is this the first time you’ve seen this error? (Y/N): Y

Steps to replicate it:

  1. Sync nextcloud using virtual filesystem.
  2. Wait until it finishes without errors.
  3. Create new folder in the synced file tree.