Вы не показываете, где вы инициализируете continueLoop со значением true и где вы изменяете его в значение false.
Вы должны показывать содержимое jmeter.log (используйте pastebin или simular-приложения), поскольку оно, безусловно, содержит важную информацию, чтобы помочьВы.
См. рабочий пример:
<?xml version="1.0" encoding="UTF-8"?>
<jmeterTestPlan version="1.2" properties="5.0" jmeter="5.1-SNAPSHOT.20181206">
<hashTree>
<TestPlan guiclass="TestPlanGui" testclass="TestPlan" testname="Test Plan" enabled="true">
<stringProp name="TestPlan.comments"></stringProp>
<boolProp name="TestPlan.functional_mode">false</boolProp>
<boolProp name="TestPlan.tearDown_on_shutdown">true</boolProp>
<boolProp name="TestPlan.serialize_threadgroups">false</boolProp>
<elementProp name="TestPlan.user_defined_variables" elementType="Arguments" guiclass="ArgumentsPanel" testclass="Arguments" testname="User Defined Variables" enabled="true">
<collectionProp name="Arguments.arguments">
<elementProp name="continueLoop" elementType="Argument">
<stringProp name="Argument.name">continueLoop</stringProp>
<stringProp name="Argument.value">true</stringProp>
<stringProp name="Argument.metadata">=</stringProp>
</elementProp>
</collectionProp>
</elementProp>
<stringProp name="TestPlan.user_define_classpath"></stringProp>
</TestPlan>
<hashTree>
<ThreadGroup guiclass="ThreadGroupGui" testclass="ThreadGroup" testname="Thread Group" enabled="true">
<stringProp name="ThreadGroup.on_sample_error">continue</stringProp>
<elementProp name="ThreadGroup.main_controller" elementType="LoopController" guiclass="LoopControlPanel" testclass="LoopController" testname="Loop Controller" enabled="true">
<boolProp name="LoopController.continue_forever">false</boolProp>
<stringProp name="LoopController.loops">1</stringProp>
</elementProp>
<stringProp name="ThreadGroup.num_threads">1</stringProp>
<stringProp name="ThreadGroup.ramp_time">1</stringProp>
<boolProp name="ThreadGroup.scheduler">false</boolProp>
<stringProp name="ThreadGroup.duration"></stringProp>
<stringProp name="ThreadGroup.delay"></stringProp>
</ThreadGroup>
<hashTree>
<WhileController guiclass="WhileControllerGui" testclass="WhileController" testname="WC" enabled="true">
<stringProp name="WhileController.condition">${__groovy(vars.get("continueLoop") == "true")}</stringProp>
</WhileController>
<hashTree>
<DebugSampler guiclass="TestBeanGUI" testclass="DebugSampler" testname="Debug Sampler" enabled="true">
<boolProp name="displayJMeterProperties">false</boolProp>
<boolProp name="displayJMeterVariables">true</boolProp>
<boolProp name="displaySystemProperties">false</boolProp>
</DebugSampler>
<hashTree/>
<TestAction guiclass="TestActionGui" testclass="TestAction" testname="Think Time" enabled="true">
<intProp name="ActionProcessor.action">1</intProp>
<intProp name="ActionProcessor.target">0</intProp>
<stringProp name="ActionProcessor.duration">0</stringProp>
</TestAction>
<hashTree>
<UniformRandomTimer guiclass="UniformRandomTimerGui" testclass="UniformRandomTimer" testname="Pause" enabled="true">
<stringProp name="ConstantTimer.delay">100</stringProp>
<stringProp name="RandomTimer.range">100</stringProp>
</UniformRandomTimer>
<hashTree/>
</hashTree>
<IfController guiclass="IfControllerPanel" testclass="IfController" testname="If Controller" enabled="true">
<stringProp name="IfController.condition">${__jexl3(${__jm__WC__idx} == 10,)}</stringProp>
<boolProp name="IfController.evaluateAll">false</boolProp>
<boolProp name="IfController.useExpression">true</boolProp>
</IfController>
<hashTree>
<TestAction guiclass="TestActionGui" testclass="TestAction" testname="Flow Control Action" enabled="true">
<intProp name="ActionProcessor.action">1</intProp>
<intProp name="ActionProcessor.target">0</intProp>
<stringProp name="ActionProcessor.duration">0</stringProp>
</TestAction>
<hashTree>
<UserParameters guiclass="UserParametersGui" testclass="UserParameters" testname="User Parameters" enabled="true">
<collectionProp name="UserParameters.names">
<stringProp name="-753878037">continueLoop</stringProp>
</collectionProp>
<collectionProp name="UserParameters.thread_values">
<collectionProp name="-544885953">
<stringProp name="97196323">false</stringProp>
</collectionProp>
</collectionProp>
<boolProp name="UserParameters.per_iteration">false</boolProp>
</UserParameters>
<hashTree/>
</hashTree>
</hashTree>
</hashTree>
</hashTree>
</hashTree>
</hashTree>
</jmeterTestPlan>