That there is a pretty high confidence level… 
I’ve not done it, however you might have a look at the forum thread referenced below and see if you can monitor the message you are seeing. I did a short test of monitoring the ‘system_event_log’ with hass-cli, seemed to confirm what the forum thread says. Not sure where your message is being posted, or if you can monitor a log other than system log. Good hunting!
Just for my curiosity, why are you not willing to share the information about the device you are having trouble with?
Automation based on log
hass-cli event watch | tee a.txt | grep "test"
10441 event_type: call_service
10442 data:
10443 domain: system_log
10444 service: write
10445 service_data:
10446 level: error
10447 message: test03
10448 origin: LOCAL
10449 time_fired: '2023-12-12T13:22:25.850280+00:00'
10450 context:
10451 id: 01HHF32TDT194FMK32SH16SG18
10452 parent_id:
10453 user_id: 0d7b429570c44c97a5ac1fe785b9d237
10454
10455 event_type: system_log_event
10456 data:
10457 name: homeassistant.components.system_log.external
10458 message:
10459 - test03
10460 level: ERROR
10461 source:
10462 - components/system_log/__init__.py
10463 - 300
10464 timestamp: 1702387345.850346
10465 exception: ''
10466 count: 1
10467 first_occurred: 1702387345.850346
10468 origin: LOCAL
10469 time_fired: '2023-12-12T13:22:25.850848+00:00'