Strange MQTT behavior for several weeks, All Clients Unavailable after reboot of HA/MQTT-Integration

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Hello fellow community members,

for several weeks now, I have been experiencing a strange behavior with my MQTT installation. Every time I restart my Home Assistant (update HACS plugins, update Home Assistant, etc.), all of my MQTT devices lose their connection and are displayed as “Unavailable.”
This also happens when I simply restart the MQTT integration in the Devices/Integrations section.

My setup is as follows:

  • Lenovo M720q with Core-i5 CPU, 16GB RAM, 2TB m.2 SSD
  • Installation Method: Home Assistant OS
  • Core: 2025.12.0
  • Supervisor: 2025.12.2
  • Operating System: 16.3
  • Frontend: 20251203.0
  • about 65 MQTT-Clients, 134 MQTT-Devices (mostly Tasmota Plugs and Zigbee2MQTT-Devices)

I’m using EMQX as an add-on in the latest version. It’s configured to allow unsecure/unauthenticated logins as I’m only using this setup locally.

My configuration has worked without any problems for years; the problems started about 6 weeks ago.

To fix the error, I first have to restart the EMQX add-on and then the remaining services that use MQTT (Zigbee2MQTT, SambaNAS, NukiHub, etc.).

There are no abnormalities visible in EMQX; the devices continue to communicate normally and appear to be connected in EMQX. I have already experimented with various settings, but none of them have resolved the issue.

I have attempted to use Mosquitto as a broker, but I am unable to get it to accept unauthenticated clients when running as an add-on.

When I look at the logs, I don’t see any relevant errors except for this one in the supervisor log after the restart:

Logger: homeassistant.util.logging
Quelle: util/logging.py:74
Erstmals aufgetreten: 07:43:28 (1 Vorkommnis)
Zuletzt protokolliert: 07:43:28

Module homeassistant.components.mqtt.number is logging too frequently. 200 messages since last count

There are a few other errors/warnings related to incorrect values in MQTT devices, but I think they are negligible here.

I have already searched the issue tracker on GitHub and also searched via Google and forums, but have not found any real help that describes my problem.

Has anyone here had similar experiences and can perhaps point me in the right direction for troubleshooting? If further logs are required, I will be happy to add them.

Thanks a lot and best regards,
Sebastian

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Crosspost: MQTT strange behaviour

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I spent the whole afternoon analyzing logs and restarting my Home Assistant and EMQX dozens of times.
It must be related in some way to EMQX or unauthorized access.
I have now installed Mosquitto, created several users, and secured all 65 of my clients.
It now works without any problems with Mosquitto. It was a lot of work, but finally I can restart HASS without having to restart dozens of other add-ons.
Maybe this will help some of you here.
Best regards,
Sebastian

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