So I just fired up a new C7...
Updated to latest HE firmware (126.96.36.199), updated the Z-wave firmware and then shutdown gracefully and pulled the plug for > 30 secs before restarting. Everything is working in it's baseline state (no devices, no apps etc). For giggles made a backup as well.
This will be a "clean slate" install with only Z-Wave devices (Zooz Dimmers and Switches) at first. Will be adding those in a few hours.
Will report back if anyone is interested to know how it went.