I'll chime in and say I have this issue too. Like 90% of my devices are zooz but I wanted an in wall outlet, so I have 2 Leviton ZW15R-1BW outlets. Like others have said, they very sporadically become completely unresponsive and the only fix is to flip the breaker to power cycle them.
One of them is only used at Christmas time to turn the tree on and off so when it stops responding the zwave mesh gets pretty messed up and the reason might not be noticeable by normal means. So I use device watchdog and if it becomes unresponsive I get notified. But it's still annoying.
I just had to do this, which prompted me to search for a firmware update and how I found this thread. Mine are also on version 1.08
