So I have been placed by this issues for a couple of years now for Haiku nightly installs using VirtualBox. So I usually get one of three issues...
1 - works fine without issue
2 - audio works, but is choppy
3 - audio not working at all
...restarting media services is a hit-n-miss affair where sometimes it'll fix it, sometimes it'll make it worse and sometimes just doesn't fix anything. After multiple reboots, it sometimes fixes itself. The thing I will say is that Haiku A4 works just fine with audio on VirtualBox. I booted multiple times into Haiku A4 this weekend and audio worked fine. Makes me suspicious that Haiku nightly has some underlying issue concerning audio that is somehow only affecting VirtualBox.