How does that work? Do you mean this? Because the Threshold Alert rule is very complicated; I wouldn’t know where to start logging 
But it sounds like “putting a rule into debug logging” is something else than adding console.log() here and there?
EDIT
This is probably what you meant. I’ll give it a try later today!
EDIT 2*
The Rule ID of my Threshold Alert rule is haarden-procesbescherming-UIT. But when I try to set the logger level in openHAB’s CLI:
openhab> log:set DEBUG org.openhab.automation.script.ui.haarden-procesbescherming-UIT
Error executing command: Unable to set level for logger
What am I doing wrong…?
EDIT 3
More importantly: I figured out why the Threshold Alert only triggered one of the rules:
2024-11-03 15:18:35.548 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'haard_eetkamer_procesbeschermingstimer' changed from 3 s to 2 s
2024-11-03 15:18:35.549 [INFO ] [hab.event.GroupItemStateChangedEvent] - Item 'haarden_procesbeschermingstimers' changed from 3 s to UNDEF through haard_eetkamer_procesbeschermingstimer
2024-11-03 15:18:35.561 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'haard_salon_procesbeschermingstimer' changed from 3 s to 2 s
2024-11-03 15:18:35.564 [INFO ] [hab.event.GroupItemStateChangedEvent] - Item 'haarden_procesbeschermingstimers' changed from UNDEF to 2 s through haard_salon_procesbeschermingstimer
2024-11-03 15:18:36.550 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'haard_eetkamer_procesbeschermingstimer' changed from 2 s to 1 s
2024-11-03 15:18:36.550 [INFO ] [hab.event.GroupItemStateChangedEvent] - Item 'haarden_procesbeschermingstimers' changed from 2 s to UNDEF through haard_eetkamer_procesbeschermingstimer
2024-11-03 15:18:36.560 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'haard_salon_procesbeschermingstimer' changed from 2 s to 1 s
2024-11-03 15:18:36.563 [INFO ] [hab.event.GroupItemStateChangedEvent] - Item 'haarden_procesbeschermingstimers' changed from UNDEF to 1 s through haard_salon_procesbeschermingstimer
2024-11-03 15:18:37.551 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'haard_eetkamer_procesbeschermingstimer' changed from 1 s to 0 s
2024-11-03 15:18:37.553 [INFO ] [hab.event.GroupItemStateChangedEvent] - Item 'haarden_procesbeschermingstimers' changed from 1 s to UNDEF through haard_eetkamer_procesbeschermingstimer
2024-11-03 15:18:37.567 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'haard_salon_procesbeschermingstimer' changed from 1 s to 0 s
2024-11-03 15:18:37.567 [INFO ] [hab.event.GroupItemStateChangedEvent] - Item 'haarden_procesbeschermingstimers' changed from UNDEF to 0 s through haard_salon_procesbeschermingstimer
2024-11-03 15:18:39.630 [INFO ] [openhab.event.ItemCommandEvent ] - Item 'haard_salon_procesbescherming' received command OFF
2024-11-03 15:18:39.631 [INFO ] [openhab.event.ItemStateChangedEvent ] - Item 'haard_salon_procesbescherming' changed from ON to OFF
2024-11-03 15:18:39.736 [INFO ] [openhab.event.ItemCommandEvent ] - Item 'haard_salon_procesbescherming' received command OFF
The group item haarden_procesbeschermingstimers was changed to 0 s by member haard_salon_procesbeschermingstimer. The fact that member haard_eetkamer_procesbeschermingstimer also changed to 0 s is apparently not registered.
So I assume in general, that if two members of the “Triggering Group” change to the same state at the same time, the Threshold Alert rule only registers one of those two triggers…?
(The reason this happens in my case, is because during openHAB startup, an ESPHome channel is switched from ON to OFF, which triggers the countdown of these timers. And there are two ESP32’s, meaning there are two ESPHome channels doing this, triggering both timeouts. I could delete the item to this particular channel, as it’s not needed, but that’s only a stopgap for this particular situation…)