Hopefully the following observation is of some interest to people.
This weekend I spent at least 8 hours tinkering with a 5.1.2 firmware turret. This post is long because I'm quite meticulous and try zillions of things when trying to solve a problem! Storage is via a Windows 8.1 PC and attempting to store data on local drives only. I tried FreeNFS, but it seemed to be flaky and regular uninitializing of drives. I then tried haneWIN and after unblocking its three exes in my firewall it worked.
But here is what really puzzled me and I'm 90% sure I've identified something that is a real thing (maybe others have and I'm super late to the party): this camera doesn't like large disks. I only stumbled upon this fact when it occurred to me, against expectations, that the only stable NAS drive I was seeing was using some old 250 GB USB drive I had running through haneWIN. After initializing this drive I've been unable to break it; the camera has been rebooted, I've turned the firewall on/off, I've yanked the cable on the PC. I've removed the drive from the camera storage tab, then re-added it. In all cases it quickly finds the drive again and continues to work.
On the contrast, whether using haneWIN's NFS, or the camera's SMB/CIFS function, when I try the same on a 1 TB drive that had 400 GB of data on it and 600 GB free, even if I could initialize (often it would fail), the best I could hope for was a couple min before it would de-initialize again. On that very same drive, I then shrunk it down to 800 GB, with a 200 GB simple drive, on its own new drive letter, hooked it up to haneWIN, and it ran all day today flawlessly. 20 minutes ago I then tried the SMB/CIFS on the original USB 250 GB drive, it initialized, and it's now been saving to the camera again. (that's a very short test so far, I agree).
In networkcameracritic's review of the Hikvision cube, some random comment by a reader speaks of a 500 GB disk causing issues, but I didn't see it anywhere else mentioned.
BTW I have my file size at the camera's default .5 GB size, even though the actual .mp4 files it creates are all 1/4GB.
At one point I did try to initialize an 8 GB drive and it failed, so there may be a minimum size as well that the drive needs to be.