ECMAScript shows error after 1 successfull run of script in Openhab

Platform information:

Hardware: Synology with docker
OS: Linux/4.4.302+ (amd64)
Java Runtime Environment: debian 17.0.12
openHAB version: openHAB 4.2.2

Issue of the topic:
I have a rule that triggers when a widget (heating) changes the setpoint of a thermostat (evohome). The script of the rule is build on ecmascript (v11). It converts some variables + item value into a stringified JSON message on the command topic of the mqtt broker . When triggered a first time, the script runs and publishes a message on the broker, and changes te setpoint.
After that, the script is ‘broken’. It takes a while, and a reinitialize of the scriptengine makes it work again 1 time. I cannot get my head around why this is happening

Tried different things, depending on the various forums i checked on topics Javascript/JSON/MQTT/Graalvm/Openhab etc, but there isn’t a specific forum that discusses mqtt with evohome on Openhab 4.
Understand that the code works, and fires successfull, but only one time.

Code build up (complete rule):

configuration: {}
triggers:
  - id: "1"
    configuration:
      itemName: Thermostaat_zone_temperature_setpoint
    type: core.ItemStateUpdateTrigger
conditions: []
actions:
  - inputs: {}
    id: "2"
    configuration:
      type: application/javascript
      script: >-
        var item = items.Thermostaat_zone_temperature_setpoint;

        var obj = new Object();

        obj.command = "set_zone_setpoint";

        obj.setpoint = item.state;

        obj.zone_idx = 1;

        obj.ctl_id = "ID";

        var val = parseFloat (obj.setpoint);

        obj.setpoint = val;

        var message = JSON.stringify(obj);

        var actions = actions.get("mqtt", "mqtt:broker:master");

        actions.publishMQTT("evohome/evogateway/_zone_independent/command",
        message);

        console.log(message);
    type: script.ScriptAction

Logging gives the following (Log when succesfull):

2024-10-17 20:17:02.354 [DEBUG] [.internal.OpenhabGraalJSScriptEngine] - Initializing GraalJS script engine...
2024-10-17 20:17:02.360 [DEBUG] [.internal.OpenhabGraalJSScriptEngine] - Injecting ThreadsafeTimers into the JS runtime...
2024-10-17 20:17:02.361 [DEBUG] [.internal.OpenhabGraalJSScriptEngine] - Evaluating cached global script...
2024-10-17 20:17:02.362 [DEBUG] [.internal.OpenhabGraalJSScriptEngine] - Evaluating cached openhab-js injection...
2024-10-17 20:17:02.417 [DEBUG] [.internal.OpenhabGraalJSScriptEngine] - Successfully initialized GraalJS script engine.
2024-10-17 20:17:02.420 [INFO ] [ab.automation.script.ui.evo_zone] - {"command":"set_zone_setpoint","setpoint":20.5,"zone_idx":1,"ctl_id":"id code"}
2024-10-17 20:17:02.420 [DEBUG] [ing.mqtt.internal.action.MQTTActions] - MQTT publish to evohome/evogateway/_zone_independent/command performed

Logging gives the following (Log when failed):

2024-10-18 06:51:42.850 [ERROR] [internal.handler.ScriptActionHandler] - Script execution of rule with UID 'evo_zone' failed: org.graalvm.polyglot.PolyglotException: TypeError: invokeMember (get) on org.openhab.binding.mqtt.internal.action.MQTTActions@27c6d6d2 failed due to: Unknown identifier: get
2024-10-18 06:54:44.350 [ERROR] [ation.script.javascript.evo_eetkamer] - Failed to execute script: TypeError: invokeMember (get) on org.openhab.binding.mqtt.internal.action.MQTTActions@27c6d6d2 failed due to: Unknown identifier: get
        at <js>.:program(<eval>:10)
        at org.graalvm.polyglot.Context.eval(Context.java:399)
        at com.oracle.truffle.js.scriptengine.GraalJSScriptEngine.eval(GraalJSScriptEngine.java:458)
        at com.oracle.truffle.js.scriptengine.GraalJSScriptEngine.eval(GraalJSScriptEngine.java:426)
        at java.scripting/javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:262)