Not able to (re)create unmanaged vault

We are using Acronis Backup & Recovery 10.0.11639.
We had to uninstall it and reinstall on the same machine and then we had to reconfigure the backups.
(We have only 4 machine, so this was not such a big problem).

There were no problem recreating backup strategies, but when we had to reconfigure the unmanaged vault, we were not able to select the same directory path of the previous configuration.
Acronis said the path we want to use was already used as an unmanaged vault, even if we completely uninstalled Acronis management Server/Console and also deleted and recreated the DB.

This error was coming up even if we tried to completely delete the previous vault's folder (including any .meta folder we found on the NAS).
As you can see from the attachments this error was also coming up both if the formerly folder exists or not.

We would like to know where does the Acronis store information about unmanaged vault, and eventually manually clean it.

Thank you.