After the last few hub updates (not sure which one it started at), my hub has been locking up almost nightly (red light on hub in morning). I finally reconnected my old smartthings hub, set up hub connect, and moved all my lightify bulbs over to it. Amazingly, the lightify bulbs seem completely happy on smartthings.
Now, the hubitat hub no longer locks up every night, but the zigbee radio disables its self 1 or 2 times a day. I then have to log into the interface and disable/enable the zigbee radio to get it back. On top of that, about half my existing sengled or tradfri lights in any room work at any given time.
This thing went from working nearly perfectly for over a year to not at all on a day-to-day basis.
I'm about to just give up and move everything back to smartthings where I know it at least worked (slower and not at all when the internet/cloud was down) but a lot more than it does currently.
What in the world could have gone wrong? Is there a bad firmware update? That's really the only thing I have changed on it, and of course setting up hubconnect.
Are these your only Zigbee devices, or do you have other Zigbee devices (like motion sensors, smart plugs, or anything else)? If so, this wouldn't explain a hub lockup, but these devices are terrible repeaters for non-bulbs and could be wreaking havoc on your Zigbee mesh. This problem is briefly summarized in Hubitat's Zigbee docs, but you can find countless forum posts with a search on this or other frequently problematic brands like Hue (when directly connected, not via the Bridge), Cree, GE Link, and others. The newest-gen Sylvania Zigbee bulbs might actually be OK, according to some users' experience, but I'm not sure anyone has really verified this with a sniffer.
But again, that wouldn't be causing a lockup (or at least I've never heard of it causing one)--just something to be aware of. Have you looked at any of the usual suspects? You've been here long enough that you may have, but I'll list a few off the top of my head just to be sure:
any custom apps or drivers?
are you using the included power supply or another of at least 5V*1A?
is the hub exposed to excessive heat? (stacked with other devices and not allowed "breathing room," in a warm environment already, etc.--some people have noticed this causes problems)
If you've already verified the above, have you contacted support? They may have additional ideas you could try or be able to determine if other resolutions may be more appropriate.
(PS - If you really do think it's the firmware, you could try downgrading: use the Diagnostic Tool, specifically the "Restore Previous Version" option. This is the formal name for the port 8081 interface you may have seen already. I haven't seen anyone mention recent firmware as being problematic in this regard, but it may still be worth a try.)
Thanks @bertabcd1234 for the suggestions. I'll go through them again and see if I can narrow it down. The hub is still in the same closet it has been when everything worked fine. Of course, it is summer now and things are hotter, but I have aimed a little fan at it and the lockups always happened at night, when temperatures are cooler.
As mentioned in the OP, I have now moved all the lightify off the hubitat hub. Even though, I still don't think they should be causing lockups.
I do have many other zigbee devices; about 8 iris outlet sockets, 2 samsung sockets, one lightify socket, 7 tradfri bulbs, about 25 sengled bulbs, 10 or so contact sensors, 5 iris motion sensors, and some other things I can't think of right now.
I just moved the three gardenspots back over to smartthings tonight. I'll see if that helps any. But I'm just ending up slowly moving everything back which is a shame.
I am using the included power supply and I haven't changed my apps in a long time. The only one being adding hubconnect and removing the echo speaks one which I was certain was causing the lockups at first.
These are the worst of the worse, great devices just horrible at repeating even them selves. I have constant issues with them at my in-laws even on the lightify hub!
It's best to have separate ZigBee meshes for all the old lamps, if you want local just get another hubitat just for problem devices. Remember ST and the like implement fixes and polling for problem devices, this gets them working but slows down your mesh and reduces it capacity. So right at the beginning HE said they would never do this, as making change like that effects everyone even if your not using it. In a ideal world all of your devices would be great quality and comply to the standards then everything would be great. Unfortunately alot of people have previous kit from other platforms that's not so great, in that case if it doesn't work well separating them often fixes that.
I've recently moved all my Zigbee to deCONZ, with a Conbee. Not because of any locking up, my hub was kind of running smooth. But because of my devices of choice (this is what I'm blaming it on mostly). I was sick and tired of pairing one minute, to have them fall off the next. This wasn't just a blip, and a weak mesh, this was over a year of toiling with the damned things.
Granted, I have a good few Xiaomi devices, but those very same devices had no issues on their own hub, the ST hub, and now on deCONZ I have 45-50 devices, and not a single drop.
Out of those I have 12 repeaters, 3 being Xbee 3's So now I'm only using one hub for Z-wave and the other for apps. So I'm kind of in the same boat I'm not sure what happened with the Zigbee on HE, but something was certainly changed, and for me it was for the worse
Sadly, out of the ones I have issues with, were all brought over from ST, where I didn't have a single issue I even bought 10 Iris motion sensors to replace the Xiaomi ones, then they started dropping too.
Im just about to increase me IKEA GU10 BULBS and considering If I should move everything first instead of getting mesh issues and having to do it all again later. I too am a Xiaomi, Tradfri hoarder
I already have two HEs, and have tried both sticks. No luck.
ST is cloud, deCONZ is local
The only times I didn't have issues were when I had loads of Tradfri on ST/HE.
I've since moved them to Hue. But the more I deal with deCONZ, the more I'm thinking about moving all my bulbs from Hue to deCONZ, and just having all Zigbee there and see how it copes with it. You can add up to 200 devices
I have 4 Ikea Tradfri GU10 bulbs.
I've tried many times to get them to "play nice" with other Zigbee devices.
I've always failed.
I also have a number of Xiaomi devices, that are on their own, separate hub. They work fine if they are the only ones on it (with Ikea repeaters). I've decided that they just aren't worth it. There are enough inexpensive Zigbee 3.0 devices just like Xiaomi, that don't require their own hub. Why go to all that bother? Why not just replace Xiaomi devices with Tuya (Zigbee 3) devices?
My Zigbee network would go offline on my main hub periodically and it was due to a bad device. An Iris plug that was really erratic - would fire events off randomly or not work at all but sometimes was fine. Was maddening until I figured it out. Bad devices can really mess things up.
I have about 12 Xiaomi Zigbee devices, about the same Samsung Smartthings devices, a few Blitzwolf Zigbee devices, and then Sonoff wifi devices. I have 3 Ikea TRADFRI repeaters and they all stay connected just fine, I am on Channel 20 on the HE and I try keep my wifi channel away from that. Touch wood no issues so far.
So the plug in question was controlling a lamp in our dining room also have a smartthings button to toggle as needed. One evening I noticed my daughter who was using the room as her "school office" kept turning on and off the lights.. she complained that the lights would come on or go off randomly. The effect on my hub was things got slow and zigbee would go offline. Of course there was never a pattern I could tell - it would just happen on occasion but other times would work fine. Swapped it out for a different Iris plug and all was well.
I also had Z-Wave device go bad - a dual switch just stopped working. That caused slow responses in some other Z-wave devices and the hub itself.
Was using the Rootn Tootn Rebootn app for a while which would reboot the hub when it detected slowness. Worked well as a stop-gap measure but was not a solution.
If you live in an area that has thunderstorms or flaky electrical one thing to consider is getting a whole home surge protector.
edit: sorry I did not have a technical way to troubleshoot the zigbee stuff.. other than the zigbee child report. I do have a conbee stick so maybe could do some fun stuff with that like zigbee sniffing.
Definitely true. With my 2 gardenspots, I could literally watch them destroy my zigbee mesh as traffic being routed through them increased to the point that they stopped repeating at all (presumably from memory exhaustion on the routing table). That is the issue - if they get too many packets flowing through them they die and quit forwarding all traffic, thus breaking any devices that happen to route through them.
This was when I had everything on zigbee2mqtt and could easily watch the mesh traffic at a low level.
They are just a badly behaving device, plain and simple. And that is not specific to Hubitat. Now I have them on their own dedicated zigbee hub, which sucks, but I don't feel like throwing them in the trash right now.
Not even considering the privacy issues involved, the cloud is horrible. My internet connection drops several times a day and there is nothing my provider can seem to do about it. Recently three days after a storm caused power outages in other neighborhoods, linemen for the power company dropped a tree on the cable providing internet service to my neighborhood. The internet was down for most of the day. I have a backup generator in case of power outages, but I don't have a backup in case of internet outages.
They may call them Wi-Fi, but they connect to somebody else's computer on the cloud, which means they behave like a dumb light bulb when the internet goes down.
I'm not sure what happened with the Zigbee on HE, but something was certainly changed, and for me it was for the worse 
I even bought 10 Iris motion sensors to replace the Xiaomi ones, then they started dropping too.
