If you still have issues with them staying paired, take a look at the channels your wifi network is running on and make sure they are not overlapping.
Mine is also running on Channel 24 which has very little overlap with my Eero setup. Wifi could interfere with them.
Just did exactly this thanks @gavincampbell. My 2.4 was set to 11, so I've moved to 6. This could have also been the reason the Xiaomi devices dropped like flies over the weekend. Still odd that my ST hub and router are roughly 3 ft away from each other, yet I didn't have any issues with that (as long as ST was up, that is!!, at least thats one issue gone 
)
I've left all devices very close to the Hub, I'll make sure they're reporting every hour overnight, then check again in the morning, before placing them where they need to be (again, 3rd time lucky perhaps?).
Cheers
Here is another idea. If you use webCoRE you can setup a pison that will monitor the xiaomi devices for you.
They all are suppose to check in every hour. And the developer put in a lastCheckIn variable that can be polled to determine this.
I wrote a piston to monitor this and then send me a notification of any devices that haven't reported in in the last 3 hours. I noticed that some will skip a few checkins but will usually check in by the 3rd or 4th hour, yet they are still online. For the record, I also see this with other no xiaomi devices I monitor as well. My sengled light bulbs for example skip a number of checkins every now and then but still are online.
I can share this piston if you are interested in it.
Thanks Gavin, I have one running too. Checks twice a day (or how many times I want). And SMS's me a list of any device setup which aren't "Active". Is yours similar, yours does sound a little more sophisticated TBH. Be glad to try if you'd like to share?
Cheers
Sounds similar but you are checking the status. I believe the status in hubitat changes to inactive if a device hasn't had an event in 24 hours. This pison will use the actual lastCheckIn.
Here it is. You can modify it as needed, may probably want to change the notification section and maybe take out the poll/refresh section. I added that step because some devices (like my dining room zwave switch) that don't get used very frequently will get changed to Inactive even though they are still online, just polling them fixes it.
Brilliant!! Many thanks Gavin. Once I can get them online, I'll give it a whirl. weCoRE is giving me a hard time due to devices taking part in Pistons, not being available. But as soon as I can, I'll be adding this!! Cheers again.
All of them still online 
How did you find out your st channel? I have one I'm trying to move over, I removed it but cant find it on HE? Will the sensor rotate through channels looking? Or if I leave it de powered will it cycle?
Its the zigbee channel on the hub's.
You have to physically change the channel yourself on the hub, the sensor won't rotate.
For ST,
log into the ide (SmartThings. Add a little smartness to your things.)
click on My Hubs, scroll down to find the ZigBee section
On the Hubitat hub, go to settings, then zigbee and it'll show you the channel you are currently on.
Hope that helps.
Thanks found it on ST
So my st is on 24 and he on 20, does the st sensors only run on 24 or can it change?
I have a couple on 20 and another one on 15.
Does the previous channel make a difference when try to re pair?
Once they are paired you can then change the channel. Give the mesh a day or so to re-route and stabilize. Remember you are changing the channel for all zigbee devices. Usually it is good to go within a few hours but some have said it took longer.
Is there a way to change the sensor channel to match HE?
They will change on their own. No need to do anything to them.
My Hubitat Elevation is using channel 20 for Zigbee and my SmartThings sensors are working well. I was on channel 14 when I was on SmartThings.
I can't pair it to HE, reading above thought the channel was the issue
What channel are you currently on for the hub? If you are on 20 then you might want to reset the sensor. I believe you can hold down the button inside until the LED blinks or goes solid then off. I can't remember. If you have the manual for it take a look and see what it says to reset it. Then try to include it again. Make sure you are within a few feet of the hub when you include it again.
Download the Hubitat app
