Julian Kessel's Blog

While testing several states (gpt,mbr,formatted,unformatted) I ran over a couple of weird errors including 1429 and a message that complained about that other programs would hold a write lock on the fs.

The final solution was the option in Vbox to turn on the USB 2.0 EHCI controller which needs the extension pack installed. On Archlinux you get it in the AUR, but you have to register it in the vbox prefs since the install script doesn’t handle this.
Instead, you can dl the extension a second time from the site, open in w/ vbox. It will register the previously installed one and give you an error because of conflicting files which is ok. After this, you can enable the EHCI controller and restoring/syncing will work fine :)