From the Reddit article that you pointed to, I see that this is not an issue specifically with VirtualBox, but it affects specific Mac models with 10.12 (Sierra). Did upgrading to 10.13 (HighSierra) fix it?
There seems to be a Parallels article that seems to reset the USB bus (
http://kb.parallels.com/en/124015). Use it at your own risk, haven't tried it (and won't) because there are no details on what it's doing. Shame for such a small program...
Also, searching a little bit more, it seems that this is a widespread problem, and a lot of solutions point to killing one (or a couple of) processes in OSX, but the basic one is:
Searching for the above line will return a gazillion of hits, specifically for the camera problem. So, I'd say that this actually might be an OSX problem, rather than a VirtualBox one. It just so happens that somehow VirtualBox triggers it, among many other applications...
That reddit article was a great find!