Just to check, did you try shutting down and unplugging for 30 seconds again after removing the zwave stick? Just to make sure the hub was once again in a neutral state.
I donāt have a C4 so maybe you have to do that regardless when removing the zwave stickā¦
I do have one other thing I think you should try. In all those screenshots, the thermostats seem to rank pretty high in your statistics. I would not only disable those, I would totally remove them for now. See if that makes any difference. I would also reenable all the other devices, and see if that makes any difference. If you have one or more devices spamming the hub, it might be causing you grief.
Oh, and are you polling these thermostats? Can you screenshot the device page for these? Which model are they?
To clarify, remove them and remove their power as well
Yep. Should have mentioned that. If a device is spamming the Zwave network, removing power from a bad device might be (is?) the only way to fix things.
Hopefully I am not jinxing myself, but I have 1 C3, 3 C4s, 1 C5 (sitting on shelf), and 1 C7.
My C3 and C4 are the workhorses in my setup. I have a C7 that I use just for development at this time. It is also my 'hot spare' should one of the other ones fail.
Thank you to all who have taken the time to reply. I have had to work so I have not had time to try all suggestions yet. Here is what I have so far.
@djw1191[quote="djw1191, post:41, topic:75476"]
Just to check, did you try shutting down and unplugging for 30 seconds again after removing the zwave stick? Just to make sure the hub was once again in a neutral state.
[/quote]I just did that this morning. I asked the hub to reboot last night but it became inaccessible. So this morning I had to pull the plug. That is a reboot without the usb zwave in. I no longer have the Severe hub CPU but both zwave (to be expected) and Zigbee are offline.
@neonturbo(Profile - neonturbo - Hubitat)[quote="neonturbo, post:42, topic:75476"]
Oh, and are you polling these thermostats? Can you screenshot the device page for these? Which model are they?
[/quote] I have not had time to try your other suggestions yet but here is a screenshot.
I had the same severe CPU use with low usage. I tried removing devices, apps etc. and am no sure why but tried turning ON my Zigbee and then turning it OFF.
The warning showed my Zigbee off (since I have no ZIgbee devices), but in settings it showed it as ON!?
having cycled the Zigbee enabled/disabled (disabled atm) all good for 48 hours now (never went a day without the warning previously.
Note: using C-5.
Things look quiet right now, load is very low. Ping me if it starts acting up again, I'll check it out.
I have had to work for 11 days straight so haven't had time to fiddle with the C4. The load should be low because there has been no z-wave stick in for at least a week. (At least that should prove that it isn't the heat of the room that was causing the severe CPU since it has been in the same spot for the week just without the zwave stick) Also I have removed every app and basically every add on that is possible. I am going to install the zwave stick and then start deleting and turning off devices. That seems to be the last step.
@sharonhouseauto Interesting suggestion. I have no zigbee devices either so I am trying it now.
Please let me know if/when it misbehaves.
It's been over a week and still good! Pretty sure this fixed the problem for me.
Would guess a bug in Hubitat software that lead to it saying Zigbee was off in the notification but was actually on is the root cause of the problem.
@sharonhouseauto That's great to hear. I hope you are all fixed. I disabled my zigbee radio too.
Here is what I have done since I last posted. I unplugged and turned off all z wave devices. Then I started turning them back on physically and in Hubitat. I have been doing one every other day or so. It was going quite well right up until it wasn't 
I plugged in one GE outdoor receptacle and activated my phone in devices so I could use the app again around the same time. Then I got a severe hub warning. I turned both the GE and my phone back off in hubitat. Then I went into Hubitat and turned off the zwave radio but that did not get the severe warning to stop. So I physically unplugged the Hubitat. It has now been up for 9 hours without the severe warning. I will wait a day or two before trying to reactivate more devices.
@gopher.ny It is still misbehaving
Could you please try turning the phone back on? It's very unlikely that phone handler produces the issue, and we can just exclude it altogether.
Is "Lights Fountain" the GE device you're referring to?
@gopher.ny Ok. I turned the phone on. Yes the "lights fountain" is the correct GE. It is physically unplugged and now deactivated in Hubitat
This is not good for your zwave mesh. Disabled devices are still in the radioās db. Unplugging a disabled device doesnāt mean the zwave radio will not be trying to route through it.
If you think it is causing issues, you should exclude the device.
@gopher.ny Hi again. I received a notice that there was an update on the Hubitat yesterday. I updated to the latest. It came online 8/3 8:11am. 8/4 6:37 am Severe Hub popped up in the log. All I did on 8/3 was turn on the whole house fan via my phone at approximately 5-7 pm. Then this morning when I woke up at 5:49am I when to the Hubitat app to turn off the fan. The app showed it was off so I didn't click anything. Later in the morning when I walked to the kitchen I heard the fan. It was still on.
@gopher.ny Severe Hub CPU came back again after the last reboot. I think I got 3 days without the error. It is still on and mostly responsive. I have not unplugged it yet.
@aaiyar I fully agree with you, the device should be deleted. However, I am first trying to diagnose Severe Hub CPU. If having a single unplugged device in the zwave mesh causes Severe Hub CPU then I think we might need the engineers to rethink the whole zwave system.
As indicated in my message, I thought you unplugged it because you thought it was responsible for the severe CPU issues (for eg. if it is something like a Zen25).
As opposed to your belief that I suggested unplugging it causes severe CPU issues. Unplugging won't do that - it will still mess with message routing in the z-wave mesh, rendering other devices unresponsive or poorly responsive.
Download the Hubitat app
