From the firmware updates link here:
One additional item, if you are using the "Leviton DZ6HD Z-Wave Dimmer" driver, I recommend switching to the "Generic Z-Wave Smart Dimmer" driver. The DZ6HD specific driver appears to have a bug in which it queries the device for updates twice rather than just once.
Note that this refers to the "Generic Z-Wave Smart Dimmer", not the "Generic Z-Wave Plus Smart Dimmer" (which should not be used with the DZ6HD).
