Your Home Assistant Zigbee network becomes unstable after adding more than 35 devices because of limited coordinator capacity, inadequate Zigbee mesh routing, channel interference, or insufficient powered Zigbee routers. Expanding the network requires adding Zigbee routers, changing to a cleaner channel, or upgrading to a more robust coordinator firmware.
Preliminary Diagnostic Steps
1. Check Coordinator Load
Open Zigbee2MQTT or Home Assistant ZHA logs and verify how
many devices are directly connected to the Sonoff dongle.
If more than 20 end devices are connected directly, the coordinator may be overloaded.
2. Measure Channel Interference
Use:
WiFi Analyzer
(Android)
inSSIDer (Windows)
to check if your Zigbee channel (e.g., 11, 15, 20, 25) overlaps with busy 2.4 GHz WiFi channels.
High overlap = unstable mesh.
3. Verify Router Count
Check how many devices are acting as Zigbee Routers (not
batterypowered).
If you have mostly battery devices, your mesh is weak and unstable.
4. Inspect Coordinator Firmware
Open your Zigbee firmware page and confirm you are running
the latest:
Sonoff Zigbee 3.0 Dongle (EFR32MG21) updated with ZStack 3.x.x (for Z2M) or the latest EZSP firmware (for ZHA).
Old firmware = instability at scale.
StepbyStep Technical Fix
1. Update Coordinator Firmware
For Zigbee2MQTT:
Install the recommended ZStack 3.x.x firmware.
For ZHA: Flash the latest EZSP > v7.4.3 firmware.
2. Switch to a Clean Zigbee Channel
1. Check WiFi congestion.
2. Change Zigbee channel in Zigbee2MQTT to:
Channel 15
Channel 20
Channel 25
3. Repair devices if required.
3. Add Zigbee Routers (Critical Step)
Install at least:
1 Zigbee router per 10 end devices
Recommended routers:
IKEA Tradfri Repeater
Sonoff ZBMINIL
Tuya Zigbee Plug Routers
This increases total stability and routing paths.
4. Reduce Direct Load on the Coordinator
In Zigbee2MQTT:
Open Map
Ensure no more than 20 devices connect directly to the coordinator.
If more:
→ Add more powered routers.
5. Use a USB Extension Cable (Important)
Move the Sonoff Dongle 50 cm away from:
WiFi routers
PC USB 3.0 ports
Metal cases
This reduces USB 3.0 interference.
Preventing Future Conflict
1. Spread Zigbee Devices Across Multiple Routers
Create a distributed mesh to prevent coordinator overload.
2. Assign Static Channel Settings
Avoid autoselect WiFi channels; manually set:
WiFi to Channel 1 or
6
Zigbee to Channel 20 or 25
3. Use a Powered USB Hub
Ensures stable voltage and eliminates USB interference.
4. Limit Direct Pairing to the Coordinator
Always pair new devices next to a router, not the dongle.
5. Keep Firmware Updated
Update:
Home Assistant
Zigbee2MQTT
ZHA
Coordinator firmware
every 2–3 months.