If you are unable to delete the folders in Shared Folders and getting the error message as shown in the screenshot above in the web UI or the message below via the CLI. This post may help with the issue.
rmdir: failed to remove 'karlo/': Device or resource busy
What worked for me was to unmount the absolute path of the directory that I need to be deleted. In my case is the folder that I created called /sharedfolders/karlo. SSH into the OMV server then execute this command:
umount /sharedfolders/karlo rm -r /sharedfolders/karlo
That’s it. Cheers!