concurrent modification exception

[ERROR] Tests run: 1, Failures: 1, Errors: 0, Skipped: 0, Time elapsed: 7.647 s <<< FAILURE! - in com.mozilla.secops.amo.TestAmo
[ERROR] amoFxaAbuseNewVersionTest on amoFxaAbuseNewVersionTest(com.mozilla.secops.amo.TestAmo)(com.mozilla.secops.amo.TestAmo)  Time elapsed: 5.854 s  <<< FAILURE!
org.apache.beam.sdk.Pipeline$PipelineExecutionException: java.util.ConcurrentModificationException
	at org.apache.beam.runners.direct.DirectRunner$DirectPipelineResult.waitUntilFinish(DirectRunner.java:348)
	at org.apache.beam.runners.direct.DirectRunner$DirectPipelineResult.waitUntilFinish(DirectRunner.java:318)
	at org.apache.beam.runners.direct.DirectRunner.run(DirectRunner.java:213)
	at org.apache.beam.runners.direct.DirectRunner.run(DirectRunner.java:67)
	at org.apache.beam.sdk.Pipeline.run(Pipeline.java:313)
	at org.apache.beam.sdk.testing.TestPipeline.run(TestPipeline.java:350)
	at org.apache.beam.sdk.testing.TestPipeline.run(TestPipeline.java:331)
	at com.mozilla.secops.amo.TestAmo.amoFxaAbuseNewVersionTest(TestAmo.java:158)
	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.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:50)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:47)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.apache.beam.sdk.testing.TestPipeline$1.evaluate(TestPipeline.java:319)
	at org.junit.rules.RunRules.evaluate(RunRules.java:20)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:325)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:78)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:57)
	at org.junit.runners.ParentRunner$3.run(ParentRunner.java:290)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:71)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:288)
	at org.junit.runners.ParentRunner.access$000(ParentRunner.java:58)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:268)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:363)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
	at org.testng.junit.JUnit4TestRunner.start(JUnit4TestRunner.java:82)
	at org.testng.junit.JUnit4TestRunner.run(JUnit4TestRunner.java:70)
	at org.testng.TestRunner$1.run(TestRunner.java:570)
	at org.testng.TestRunner.runJUnitWorkers(TestRunner.java:717)
	at org.testng.TestRunner.privateRunJUnit(TestRunner.java:601)
	at org.testng.TestRunner.run(TestRunner.java:502)
	at org.testng.SuiteRunner.runTest(SuiteRunner.java:455)
	at org.testng.SuiteRunner.runSequentially(SuiteRunner.java:450)
	at org.testng.SuiteRunner.privateRun(SuiteRunner.java:415)
	at org.testng.SuiteRunner.run(SuiteRunner.java:364)
	at org.testng.SuiteRunnerWorker.runSuite(SuiteRunnerWorker.java:52)
	at org.testng.SuiteRunnerWorker.run(SuiteRunnerWorker.java:84)
	at org.testng.TestNG.runSuitesSequentially(TestNG.java:1187)
	at org.testng.TestNG.runSuitesLocally(TestNG.java:1116)
	at org.testng.TestNG.runSuites(TestNG.java:1028)
	at org.testng.TestNG.run(TestNG.java:996)
	at org.apache.maven.surefire.testng.TestNGExecutor.run(TestNGExecutor.java:135)
	at org.apache.maven.surefire.testng.TestNGDirectoryTestSuite.executeSingleClass(TestNGDirectoryTestSuite.java:112)
	at org.apache.maven.surefire.testng.TestNGDirectoryTestSuite.execute(TestNGDirectoryTestSuite.java:99)
	at org.apache.maven.surefire.testng.TestNGProvider.invoke(TestNGProvider.java:146)
	at org.apache.maven.surefire.booter.ForkedBooter.invokeProviderInSameClassLoader(ForkedBooter.java:384)
	at org.apache.maven.surefire.booter.ForkedBooter.runSuitesInProcess(ForkedBooter.java:345)
	at org.apache.maven.surefire.booter.ForkedBooter.execute(ForkedBooter.java:126)
	at org.apache.maven.surefire.booter.ForkedBooter.main(ForkedBooter.java:418)
Caused by: java.util.ConcurrentModificationException
	at java.util.ArrayList.writeObject(ArrayList.java:770)
	at sun.reflect.GeneratedMethodAccessor9.invoke(Unknown Source)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.lang.reflect.Method.invoke(Method.java:498)
	at java.io.ObjectStreamClass.invokeWriteObject(ObjectStreamClass.java:1140)
	at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1496)
	at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
	at java.io.ObjectOutputStream.defaultWriteFields(ObjectOutputStream.java:1548)
	at java.io.ObjectOutputStream.writeSerialData(ObjectOutputStream.java:1509)
	at java.io.ObjectOutputStream.writeOrdinaryObject(ObjectOutputStream.java:1432)
	at java.io.ObjectOutputStream.writeObject0(ObjectOutputStream.java:1178)
	at java.io.ObjectOutputStream.writeObject(ObjectOutputStream.java:348)
	at org.apache.beam.sdk.coders.SerializableCoder.encode(SerializableCoder.java:183)
	at org.apache.beam.sdk.coders.SerializableCoder.encode(SerializableCoder.java:53)
	at org.apache.beam.sdk.coders.Coder.encode(Coder.java:136)
	at org.apache.beam.sdk.coders.KvCoder.encode(KvCoder.java:71)
	at org.apache.beam.sdk.coders.KvCoder.encode(KvCoder.java:36)
	at org.apache.beam.sdk.util.CoderUtils.encodeToSafeStream(CoderUtils.java:82)
	at org.apache.beam.sdk.util.CoderUtils.encodeToByteArray(CoderUtils.java:66)
	at org.apache.beam.sdk.util.CoderUtils.encodeToByteArray(CoderUtils.java:51)
	at org.apache.beam.sdk.util.MutationDetectors$CodedValueMutationDetector.<init>(MutationDetectors.java:116)
	at org.apache.beam.sdk.util.MutationDetectors.forValueWithCoder(MutationDetectors.java:44)
	at org.apache.beam.runners.direct.ImmutabilityCheckingBundleFactory$ImmutabilityEnforcingBundle.add(ImmutabilityCheckingBundleFactory.java:112)
	at org.apache.beam.runners.direct.ParDoEvaluator$BundleOutputManager.output(ParDoEvaluator.java:264)
	at org.apache.beam.repackaged.beam_runners_direct_java.runners.core.SimpleDoFnRunner.outputWindowedValue(SimpleDoFnRunner.java:248)
	at org.apache.beam.repackaged.beam_runners_direct_java.runners.core.SimpleDoFnRunner.access$700(SimpleDoFnRunner.java:74)
	at org.apache.beam.repackaged.beam_runners_direct_java.runners.core.SimpleDoFnRunner$DoFnProcessContext.output(SimpleDoFnRunner.java:560)
	at org.apache.beam.sdk.transforms.DoFnOutputReceivers$WindowedContextOutputReceiver.output(DoFnOutputReceivers.java:71)
	at org.apache.beam.sdk.transforms.MapElements$1.processElement(MapElements.java:139)

[INFO]
[INFO] Results:
[INFO]
[ERROR] Failures:
[ERROR]   TestAmo.amoFxaAbuseNewVersionTest:158 » PipelineExecution java.util.Concurrent...
[INFO]
[ERROR] Tests run: 1, Failures: 1, Errors: 0, Skipped: 0
[INFO]
[INFO] ------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] ------------------------------------------------------------------------
[INFO] Total time:  21.314 s
[INFO] Finished at: 2019-07-19T20:28:00Z
[INFO] ------------------------------------------------------------------------