What driver are you using for the devices? I have a published custom driver for that device, not sure if it will help. [DRIVER] Leviton Dimmers (DZPD3 / DZ6HD)
Also, please post a screenshot of your rule(s)
The C8 does not have any better CPU or Memory than the C7, but it does have a better Zwave chip and external antenna so possibly that may help.
More than likely though it can be made to work by tweaking some things in your rule.
