Zigbee devices keep dropping off Home Assistant — what's actually causing it (and how to fix it)

[Ishara Fernando]

One of the most common frustrations in the Home Assistant community right now: Zigbee devices that pair fine, work for a day or two, then drop off and show as unavailable, sometimes coming back on their own, sometimes not.
The generic answer you'll find everywhere is "improve your mesh." That's not wrong, but it's not useful on its own. Here's what's actually worth checking, in order:

1. Coordinator placement first, mesh second
   The coordinator is the root of the entire Zigbee mesh. If it's plugged directly into a USB port on your Home Assistant machine, USB 3.0 interference is a likely culprit. It broadcasts in the 2.4GHz range and drowns out Zigbee signals. Fix: use a USB 2.0 extension cable (1–2 metres) to move the coordinator away from the machine. This alone solves the problem for a large number of people.

2. Powered devices vs. battery devices
   Battery-powered devices (sensors, buttons) are end devices — they don't route traffic. Only mains-powered devices (plugs, bulbs) act as routers and extend your mesh. If most of your devices are battery-powered, your mesh has almost no routing capacity. Add at least 2–3 mains-powered devices within range of the coordinator before assuming anything else is broken.

3. Channel conflicts with Wi-Fi
   Zigbee and 2.4GHz Wi-Fi share spectrum. Zigbee channels 11–13 overlap heavily with Wi-Fi channel 1; Zigbee channels 25–26 overlap with Wi-Fi channel 11. If you haven't set your Zigbee channel deliberately, check what your Wi-Fi is using and pick a Zigbee channel that doesn't overlap. Zigbee channel 15, 20, or 25 are usually the safest depending on your Wi-Fi setup.

4. ZHA vs. Zigbee2MQTT coordinator handling
   Both ZHA and Zigbee2MQTT handle coordinator recovery differently after a Home Assistant restart or power cut. If devices drop specifically after HA restarts, check whether your coordinator firmware is current — outdated firmware on Sonoff Zigbee 3.0 USB dongles in particular is a known cause of post-restart drops.

5. Check LQI before assuming range
   In Zigbee2MQTT, go to the map view and look at the LQI (Link Quality Indicator) values on the connections to your dropping devices. Anything below 50 is weak; below 20 is effectively broken. This tells you whether it's a range/routing problem or something else entirely.

What coordinator are you running, and are the drops happening on specific device types or randomly across the mesh? Drop your setup below, happy to help diagnose.