Title says it all...wondering if I there is any reason I should not turn off the hub for 20m and restart to induce zigbee panic mode and speed up devices rerouting.
Any problem w/that?
(Other than it shows that I almost have the patience of a four year old.)
I have very few Zigbee devices on the hub, just two "active" devices actually, aside from four Tradifi Ikea plug/repeaters.
I'm not a Zigbee expert but I would guess changing channel has already put your devices in the panic mode since all of a sudden there is no longer a hub they have been talking to.
Having said that, your post was 21 minutes ago, if you had shutdown the hub before you posted, you would be all done by now. IMHO shutting down the hub (properly) can never be bad. It might not accomplish much but it cannot hurt.
Figured the same, but never changed channels before and didn't know if there might be any compound effects. 
Some devices could take a day to move over, especially sleepy devices that don’t wake up that often. You can always expedite the process by resetting the device and start pairing mode on the hub. It will fall back in place immediately.
When I changed the channel on my C-5s, everything on both hubs immediately recognized the change except the Hue dimmers. I had to reset and rejoin them.
Download the Hubitat app
