The new recovery Stick has the option to update just reinstall the hypervisor on its partition without touching the VM storage space.
To do that, you can follow the Guide: Factory Reset and Recovery - Appliance, BNTA20/BNTA21/BNTA22 until you reach the Web-GUI of the recovery Stick. Choose the latest "HV-Only" Appliance OS, e.g.:
Appliance-OS-1.0.1-HV-only
And install it. It will maintain your VMs but reset the Hypervisor OS.
NOTE: if your hypervisor was updated from 0.9.9 or 1.0 to 1.01 or later you will see the below message and you will need to recover your Hypervisor with the above Steps and the USB-Stick
