Parallels 9 changes Sharing settings on its own.

Parallels 9 with a Windows 7 64-bit VM on a 10.8.5, fully patched iMac.

We've turned off all of the Sharing settings on the VM, sharing only the Documents folder on the Mac. This means that we have Share Folders: set to None, with Custom Folders... pointing at the user's Documents folder.

Twice now, we've had to change the setting for Share Folders back to None. Parallels 9 seems to arbitrarily switch it back to "All Disks" without intervention from the user. We only notice the change when the user notices two additional network shares in Windows Explorer.

Any idea what's causing this to happen? The user is non-technical and is certain they've never touched any of the settings, let alone the Share Folders setting.

Edit: All other Sharing settings have been turned off.

And if not, any idea how to prevent this from ever changing again?