How can a rule trigger a switch on sitemap!?

Unfortunately this doesn’t work!

rule

rule "manuelle Wonzimmer-Heizung"
when
	Item Wohnzimmer_Heizung received command
then
	if (Wohnzimmer_Heizung.state == ON)
	{
	Heizung_Wohnzimmer_Stellgroesse.sendCommand(100)
	logInfo("Heizung", "WEB: Wohnzimmer = 100% für 60 min")
	

		timerWohnzimmer = createTimer(now.plusMinutes(2))
		[|	
		Heizung_Wohnzimmer_Stellgroesse.sendCommand(0)
		logInfo("Heizung", "WEB: Wohnzimmer Auto = 0%")
		Heizung_Wohnzimmer.postUpdate(OFF)
		]	
	}

sitemap

			Frame label="Heizungs-Schaltung 60 min."
			{
			Switch item=Duschbad_Heizung
			Switch item=Wohnzimmer_Heizung
			}

items

// Heizung virt. Schalter
Switch 		Duschbad_Heizung			"Duschbad Heizung"			<heating>	
Switch 		Wohnzimmer_Heizung			"Wohnzimmer Heizung"			<heating>					

Dimmer Heizung_Duschbad_Stellgroesse 	"Heizung Duschbad Stellwert [%d %%]"		<heating> 		{knx="<5.001:3/1/8"}
Dimmer Heizung_Wohnzimmer_Stellgroesse 	"Heizung Wohnzimmer Stellwert [%d %%]"		<heating> 		{knx="<5.001:3/1/1"}

log

2016-10-30 08:14:19.092 [INFO ] [c.internal.ModelRepositoryImpl] - Refreshing model 'Heizung.rules'
2016-10-30 08:14:51.346 [INFO ] [g.openhab.model.script.Heizung] - WEB: Wohnzimmer = 100% für 60 min
2016-10-30 08:14:51.737 [ERROR] [o.o.c.s.ScriptExecutionThread ] - Error during the execution of rule 'manuelle Wonzimmer-Heizung': org.eclipse.xtext.util.PolymorphicDispatcher$NoSuchMethodException: Couldn't find method ''_assignValue'' for objects [JvmVoid:  (eProxyURI: Heizung.rules#xtextLink_::0.2.7.2.0.0.1.0.3::0::/1), <null> timerWohnzimmer <XFeatureCallImplCustom>, org.openhab.model.script.internal.actions.TimerImpl@1f7d2df, org.eclipse.xtext.xbase.interpreter.impl.DefaultEvaluationContext@fb645f, org.eclipse.xtext.util.CancelIndicator$1@5a163]
2016-10-30 08:16:51.817 [INFO ] [g.openhab.model.script.Heizung] - WEB: Wohnzimmer Auto = 0%

Could this help to find the problem?