That's interesting, I usually treat the ability of easily snapshotting and restoring virtual machines as one of the main reasons for doing things inside a VM.
I believe some of the Ubuntu ones would occasionally just not recover correctly, some kind of video-card issue most likely.
In any case, Win10 did not signal VirtualBox to save state -- or else didn't give it enough time -- so I would occasionally come back to my office to find everything I was working on gone due to some mystery-reboot that I didn't recall scheduling.
