Modbus timing-out after 2023.12.3

My Modbus to my SMA inverter has been very stable and I haven’t changed anything about it. I updated the HA Core from 2023.11.3 to 2023.12.3 on 18 Dec, then at around 4am on 19 Dec, the Modbus stopped working (timeouts). I fiddled around (re-booting etc) and it came good. However, during reboots (which took much longer than usual, I was getting “Something is blocking Home Assistant from wrapping up the start up phase. We’re going to continue anyway” in the Logfile.

This morning (also just after 4am), the Modbus went down again. Reboots have been giving the “Something is blocking Home Assistant from wrapping up the start up phase” error in the log again, and I haven’t been able to coax the Modbus into life.

The HA Core Logs show:
Logger: homeassistant.components.modbus.modbus
Source: components/modbus/
Integration: Modbus (documentation, issues)
First occurred: 3:19:23 PM (1 occurrences)
Last logged: 3:19:23 PM
Pymodbus: SMA: Error: device: 3 address: 30775 → Modbus Error: [Connection]
Failed to connect[ModbusTcpClient(]

  • which doesn’t give me any clue why it’s not connecting.

I downgraded the Core back to 2023.11.3 but that did not fix the problem.

Same here. I have a custom integration I wrote which which leverages the modbus integration. I am using serial modbus. I’ve noticed the same issues as yours when updating from 2023.11.something to 2023.12.3. I’m using RPi 3 with HASS OS. Rolled back didn’t fix things.

Definitely something has changed somewhere. By looking and the issue tracker in github seems like other people has had the same issue, but every issue was dismissed in one way or another. Maybe the changes aren’t in modbus but something underneath.

After getting timeouts from some Windows-based Modbus server test software, I power-cycled the inverter itself, it came good and I have had no more outages.