interesting. theirs are pretty much the only reliable sensors I found

That's weird to me. I have 30 aqara devices and they only drop off the network when the controller is missing (ConBee stick).

My first zigbee device was Sylvania (73685) rgbw led strip. On it's own it worked fine but once I started trying to add sengled zigbee bulbs I kept having problems with pairing the bulbs or keeping them connected. Zigbee uses 2.4ghz so I thought maybe interference so lowered power output on wifi AP 2.4ghz band & even turned it off for testing but didn't help. I think I read somewhere that sylvanias caused that problem. I unplugged sylvania led strip, reset & rejoined everything else and had zero problems. Tried to add the sylvania back in and disconnect problems came back after awhile. It was past the return period so now I keep it unjoined and plugged into a zigbee smart outlet. I sometimes have to remove power from it to join new devices or when I restart zigbee controller. Currently have mix of sengled bulbs, thirdreality plugs, sonoff plugs & sensors, and single aqara tvoc all working together fairly reliably.

If you happen to use a Conbee II: I had this issue until I updated the firmware. Has been rock solid with aqara devices after that.

Fortunately my thermometers don’t do that, because they are a good choice, Zigbee wise. Always on the lookout for replacements, if the need arises…

may wanna check your wifi & zigbee network collisions, your network map or make sure you don't something like a 2nd hub or something like that

Aqara devices can be finicky with non-Aqara devices, especially router devices.

I've personally also had much better results with Aqara devices since switching to Zigbee2MQTT and a Sonoff Zigbee stick, I had a lot more dropouts with ZHA and a Conbee II stick.