Danfoss Ally eTRV0103 disconnecting regularly

[soframel]

Hello,

I have a problem with some thermostats "Danfoss Ally eTRV0103" that are regularly disconnected/lost from zigbee2mqtt. It is probably because of the devices in themselves, because I also had issues in my previous setup (with a Conbee II + OpenHab), but I am wondering what I could do to improve their stability in my current setup (I have a SONOFF Zigbee Gateway "ZBDongle-E", zigbee2mqtt and HomeAssistant):

It is clearly related to routing, because the devices disappearing are the ones further away from the controller (controller is on the ground floor, the problematic thermostats are on the second floor), whereas the thermostats from the first floor work fine. Some devices are used for repeating/relaying the signal (depending on the time, one or two power plugs, and according to the map, a programmable switch in the wall is also often used for routing).

I have 6 of these thermostats (5 eTRV0103 and 1 of eTRV0100, but this last one is working fine, on the 1rst floor).

The devices disappear from zigbee2mqtt. The errors in the logs are from some of them just that they left the network:
[2025-12-27 22:32:18] warning: z2m: Device 'thermostatSdb2' left the network

with from time to time these kinds of errors:
[2025-12-27 22:32:18] info: zh:ember:ezsp: Received network/route error ROUTE_ERROR_SOURCE_ROUTE_FAILURE for "45907".

But for one device (the one that disconnects the most regularly), I get 8 ROUTE_ERROR_SOURCE_ROUTE_FAILURE errors like this (6 errors, then a few message and a log that the device left the network, then 2 errors, then zigbee2mqtt seems to restart! See the complete log below):
[2025-12-27 17:49:23] info: zh:ember:ezsp: Received network/route error ROUTE_ERROR_SOURCE_ROUTE_FAILURE for "48647".

What could I do to improve this ? should I at least change a configuration to prevent zigbee2mqtt from restarting? Is there way to reconnect the devices automatically?
Perhaps a better signal repeater could help, but how could I prevent existing plugs or switches from being used as repeaters?
(I have started adding automations in HomeAssistant to send notifications in case the device is in state unknown or unavailable, but this only seems to work for the device that makes zigbee2mqtt restart, and it is triggered very often. It does not work for the devices that simply disappear, for them the temperatures values just stay constant in homeassisant, and I don't know how I could detect this...).

Zigbee2mqtt is running on a Raspberry Pi with a HomeAssistant OS installation, updated to the latest version.
Zigbee2MQTT HOA Addon Config:

data_path: /config/zigbee2mqtt
socat:
  enabled: false
  master: pty,raw,echo=0,link=/tmp/ttyZ2M,mode=777
  slave: tcp-listen:8485,keepalive,nodelay,reuseaddr,keepidle=1,keepintvl=1,keepcnt=5
  options: "-d -d"
  log: false
mqtt:
  last_seen: ISO_8601_local
serial:
  port: /dev/ttyUSB0
  adapter: ember

Example log of devices disconnected:

[2025-12-27 22:32:18] warning: 	z2m: Device 'thermostatSdb2' left the network
[2025-12-27 22:32:18] info: 	z2m:mqtt: MQTT publish: topic 'zigbee2mqtt/bridge/event', payload '{"data":{"friendly_name":"thermostatSdb2","ieee_address":"0x70ac08fffe5516dc"},"type":"device_leave"}'
[2025-12-27 22:32:18] info: 	zh:ember:ezsp: Received network/route error ROUTE_ERROR_SOURCE_ROUTE_FAILURE for "45907".

Example log of the device with zigbee2mqtt restart:
thermostat-unavailable-20251227.log