Could not find proper message validator for message type 'json', please define a capable message validator for this message type

**Citrus Version**
2.8.0, tests are in XML files

**Question**
I've encountered an unusual problem while conducting integration tests using Citrus. During multiple runs of the same test, I'm consistently encountering an error that looks something like this:

`com.consol.citrus.exceptions.TestCaseFailedException: Could not find proper message validator for message type 'json', please define a capable message validator for this message type
at com.consol.citrus.TestCase.executeAction(TestCase.java:227)
at com.consol.citrus.TestCase.doExecute(TestCase.java:152)
at com.consol.citrus.actions.AbstractTestAction.execute(AbstractTestAction.java:42)
at com.consol.citrus.Citrus.run(Citrus.java:403)
at com.consol.citrus.testng.AbstractTestNGCitrusTest.invokeTestMethod(AbstractTestNGCitrusTest.java:131)
at com.consol.citrus.testng.AbstractTestNGCitrusTest.run(AbstractTestNGCitrusTest.java:108)
at com.consol.citrus.testng.AbstractTestNGCitrusTest.run(AbstractTestNGCitrusTest.java:70)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:498)
at org.testng.internal.MethodInvocationHelper.invokeHookable(MethodInvocationHelper.java:212)
at org.testng.internal.Invoker.invokeMethod(Invoker.java:707)
at org.testng.internal.Invoker.invokeTestMethod(Invoker.java:901)
at org.testng.internal.Invoker.invokeTestMethods(Invoker.java:1231)
at org.testng.internal.TestMethodWorker.invokeTestMethods(TestMethodWorker.java:127)
at org.testng.internal.TestMethodWorker.run(TestMethodWorker.java:111)
at org.testng.TestRunner.privateRun(TestRunner.java:767)
at org.testng.TestRunner.run(TestRunner.java:617)
at org.testng.SuiteRunner.runTest(SuiteRunner.java:348)
at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:343)
at org.testng.SuiteRunner.privateRun(SuiteRunner.java:305)
at org.testng.SuiteRunner.run(SuiteRunner.java:254)
at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:86)
at org.testng.TestNG.runSuitesSequentially(TestNG.java:1224)
at org.testng.TestNG.runSuitesLocally(TestNG.java:1149)
at org.testng.TestNG.run(TestNG.java:1057)
at org.apache.maven.surefire.testng.TestNGExecutor.run(TestNGExecutor.java:115)
at org.apache.maven.surefire.testng.TestNGDirectoryTestSuite.executeMulti(TestNGDirectoryTestSuite.java:204)
at org.apache.maven.surefire.testng.TestNGDirectoryTestSuite.execute(TestNGDirectoryTestSuite.java:107)
at org.apache.maven.surefire.testng.TestNGProvider.invoke(TestNGProvider.java:112)
at org.apache.maven.surefire.booter.ForkedBooter.invokeProviderInSameClassLoader(ForkedBooter.java:200)
at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:153)
at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:103)`

This issue seems to occur intermittently and I'm uncertain about the root cause. Has anyone else experienced a similar problem with Citrus integration tests? Any insights or suggestions on how to troubleshoot or mitigate this recurring error would be greatly appreciated.

Thanks in advance!

**What I've tried so far**

**Additional information**

Start with the XML integration tests and the failure at TestCase.executeAction in Citrus 2.8.0. Reproduce the repeated test runs and trace how the JSON message validator is selected or reported as missing. Done means the cause is identified and JSON messages consistently use a capable validator, with the relevant test coverage updated.

Written by the indexing model from the issue text.