Blockly "contextual info" "previous state of item" as String fails

Coming back on this one. I’m on OH 4.1.

I’m trying to work with the block “contextual info”-block.

Here’s my test case:
image

The rule is triggered in this test case by a change of a switch:

While the first block runs through like it should…
2023-12-26 14:08:52.372 [ERROR] [ab.automation.script.ui.test_blockly] - OFF

… the second block always throws an error:

2023-12-26 14:08:52.372 [ERROR] [b.automation.script.javascript.stack] - Failed to execute script:
org.graalvm.polyglot.PolyglotException: TypeError: undefined has no such function "toString"
	at <js>.:program(<eval>:2) ~[?:?]
	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 javax.script.AbstractScriptEngine.eval(AbstractScriptEngine.java:262) ~[java.scripting:?]
	at org.openhab.automation.jsscripting.internal.scriptengine.DelegatingScriptEngineWithInvocableAndAutocloseable.eval(DelegatingScriptEngineWithInvocableAndAutocloseable.java:53) ~[?:?]
	at org.openhab.automation.jsscripting.internal.scriptengine.InvocationInterceptingScriptEngineWithInvocableAndAutoCloseable.eval(InvocationInterceptingScriptEngineWithInvocableAndAutoCloseable.java:78) ~[?:?]
	at org.openhab.automation.jsscripting.internal.scriptengine.DelegatingScriptEngineWithInvocableAndAutocloseable.eval(DelegatingScriptEngineWithInvocableAndAutocloseable.java:53) ~[?:?]
	at org.openhab.automation.jsscripting.internal.scriptengine.InvocationInterceptingScriptEngineWithInvocableAndAutoCloseable.eval(InvocationInterceptingScriptEngineWithInvocableAndAutoCloseable.java:78) ~[?:?]
	at org.openhab.core.automation.module.script.internal.handler.ScriptActionHandler.lambda$0(ScriptActionHandler.java:71) ~[?:?]
	at java.util.Optional.ifPresent(Optional.java:178) [?:?]
	at org.openhab.core.automation.module.script.internal.handler.ScriptActionHandler.execute(ScriptActionHandler.java:68) [bundleFile:?]
	at org.openhab.core.automation.internal.RuleEngineImpl.executeActions(RuleEngineImpl.java:1188) [bundleFile:?]
	at org.openhab.core.automation.internal.RuleEngineImpl.runRule(RuleEngineImpl.java:997) [bundleFile:?]
	at org.openhab.core.automation.internal.TriggerHandlerCallbackImpl$TriggerData.run(TriggerHandlerCallbackImpl.java:87) [bundleFile:?]
	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:539) [?:?]
	at java.util.concurrent.FutureTask.run(FutureTask.java:264) [?:?]
	at java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:304) [?:?]
	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1136) [?:?]
	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635) [?:?]
	at java.lang.Thread.run(Thread.java:840) [?:?]
2023-12-26 14:08:52.373 [ERROR] [internal.handler.ScriptActionHandler] - Script execution of rule with UID 'test_blockly' failed: org.graalvm.polyglot.PolyglotException: TypeError: undefined has no such function "toString"

The rule is definitely triggered by a change or update event, as suggested by @rlkoshak, so I believe this is not the root cause for failure.

I wonder whether this is a bug (I read this one here)? Or am I missing something really obvious?

Anyone having an idea?