SkinxTest.testJavascriptExtension is flickering

org.openqa.selenium.NoSuchElementException: 
Unable to locate element: //*[contains(@class, 'selectize-dropdown') and contains(@class, 'active')]//*[contains(@class, 'xwiki-selectize-option') and @data-value = 'XWiki.JavaScriptExtension']
For documentation on this error, please visit: https://www.seleniumhq.org/exceptions/no_such_element.html
Build info: version: '3.141.59', revision: 'e82be7d358', time: '2018-11-14T08:17:03'
System info: host: 'a87465328f4d', ip: '172.17.0.2', os.name: 'Linux', os.arch: 'amd64', os.version: '4.9.165-xxxx-std-ipv6-64', java.version: '1.8.0_232'
Driver info: org.openqa.selenium.firefox.FirefoxDriver
Capabilities {acceptInsecureCerts: true, browserName: firefox, browserVersion: 69.0.3, javascriptEnabled: true, moz:accessibilityChecks: false, moz:buildID: 20191009172106, moz:geckodriverVersion: 0.26.0, moz:headless: false, moz:processID: 1059, moz:profile: /tmp/rust_mozprofileIRjpT2, moz:shutdownTimeout: 60000, moz:useNonSpecCompliantPointerOrigin: false, moz:webdriverClick: true, pageLoadStrategy: normal, platform: LINUX, platformName: LINUX, platformVersion: 4.9.165-xxxx-std-ipv6-64, rotatable: false, setWindowRect: true, strictFileInteractability: false, timeouts: {implicit: 0, pageLoad: 300000, script: 30000}, unhandledPromptBehavior: dismiss and notify}
Session ID: 470ad788-385a-4759-b5c9-050143ab8ea2
*** Element info: {Using=xpath, value=//*[contains(@class, 'selectize-dropdown') and contains(@class, 'active')]//*[contains(@class, 'xwiki-selectize-option') and @data-value = 'XWiki.JavaScriptExtension']}
	at sun.reflect.GeneratedConstructorAccessor39.newInstance(Unknown Source)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
	at org.openqa.selenium.remote.http.W3CHttpResponseCodec.createException(W3CHttpResponseCodec.java:187)
	at org.openqa.selenium.remote.http.W3CHttpResponseCodec.decode(W3CHttpResponseCodec.java:122)
	at org.openqa.selenium.remote.http.W3CHttpResponseCodec.decode(W3CHttpResponseCodec.java:49)
	at org.openqa.selenium.remote.HttpCommandExecutor.execute(HttpCommandExecutor.java:158)
	at org.openqa.selenium.remote.service.DriverCommandExecutor.execute(DriverCommandExecutor.java:83)
	at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:552)
	at org.openqa.selenium.remote.RemoteWebDriver.findElement(RemoteWebDriver.java:323)
	at org.openqa.selenium.remote.RemoteWebDriver.findElementByXPath(RemoteWebDriver.java:428)
	at org.openqa.selenium.By$ByXPath.findElement(By.java:353)
	at org.openqa.selenium.remote.RemoteWebDriver.findElement(RemoteWebDriver.java:315)
	at org.xwiki.test.ui.XWikiWebDriver.findElement(XWikiWebDriver.java:689)
	at org.xwiki.test.ui.XWikiWebDriver.findElementWithoutWaiting(XWikiWebDriver.java:90)
	at org.xwiki.test.ui.po.SuggestInputElement.selectByValue(SuggestInputElement.java:229)
	at org.xwiki.test.ui.po.editor.ObjectEditPage.addObject(ObjectEditPage.java:59)
	at org.xwiki.test.ui.SkinxTest.testJavascriptExtension(SkinxTest.java:68)
	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:59)
	at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
	at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:56)
	at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.xwiki.test.ui.AuthenticationRule$1.evaluate(AuthenticationRule.java:73)
	at org.xwiki.test.ui.browser.BrowserTestRule$1.evaluate(BrowserTestRule.java:104)
	at org.junit.rules.TestWatcher$1.evaluate(TestWatcher.java:61)
	at org.junit.rules.TestWatcher$1.evaluate(TestWatcher.java:61)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.BlockJUnit4ClassRunner$1.evaluate(BlockJUnit4ClassRunner.java:100)
	at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:366)
	at org.junit.runners.BlockJUnit4ClassRunner.runChild(BlockJUnit4ClassRunner.java:103)
	at com.google.code.tempusfugit.concurrency.IntermittentTestRunner.runChild(IntermittentTestRunner.java:36)
	at com.google.code.tempusfugit.concurrency.IntermittentTestRunner.runChild(IntermittentTestRunner.java:25)
	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
	at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
	at org.junit.internal.runners.statements.RunAfters.evaluate(RunAfters.java:27)
	at org.xwiki.test.integration.junit4.ValidateConsoleRule$ValidateConsoleStatement.evaluate(ValidateConsoleRule.java:73)
	at org.junit.rules.RunRules.evaluate(RunRules.java:20)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
	at org.junit.runners.Suite.runChild(Suite.java:128)
	at org.junit.runners.Suite.runChild(Suite.java:27)
	at org.junit.runners.ParentRunner$4.run(ParentRunner.java:331)
	at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:79)
	at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:329)
	at org.junit.runners.ParentRunner.access$100(ParentRunner.java:66)
	at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:293)
	at org.junit.runners.ParentRunner$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
	at org.junit.extensions.cpsuite.ClasspathSuite.run(ClasspathSuite.java:194)
	at org.xwiki.test.integration.XWikiExecutorSuite.run(XWikiExecutorSuite.java:195)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
	at org.junit.vintage.engine.execution.RunnerExecutor.execute(RunnerExecutor.java:43)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.accept(ForEachOps.java:183)
	at java.util.stream.ReferencePipeline$3$1.accept(ReferencePipeline.java:193)
	at java.util.Iterator.forEachRemaining(Iterator.java:116)
	at java.util.Spliterators$IteratorSpliterator.forEachRemaining(Spliterators.java:1801)
	at java.util.stream.AbstractPipeline.copyInto(AbstractPipeline.java:482)
	at java.util.stream.AbstractPipeline.wrapAndCopyInto(AbstractPipeline.java:472)
	at java.util.stream.ForEachOps$ForEachOp.evaluateSequential(ForEachOps.java:150)
	at java.util.stream.ForEachOps$ForEachOp$OfRef.evaluateSequential(ForEachOps.java:173)
	at java.util.stream.AbstractPipeline.evaluate(AbstractPipeline.java:234)
	at java.util.stream.ReferencePipeline.forEach(ReferencePipeline.java:485)
	at org.junit.vintage.engine.VintageTestEngine.executeAllChildren(VintageTestEngine.java:82)
	at org.junit.vintage.engine.VintageTestEngine.execute(VintageTestEngine.java:73)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:248)
	at org.junit.platform.launcher.core.DefaultLauncher.lambda$execute$5(DefaultLauncher.java:211)
	at org.junit.platform.launcher.core.DefaultLauncher.withInterceptedStreams(DefaultLauncher.java:226)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:199)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:132)
	at org.apache.maven.surefire.junitplatform.JUnitPlatformProvider.invokeAllTests(JUnitPlatformProvider.java:150)
	at org.apache.maven.surefire.junitplatform.JUnitPlatformProvider.invoke(JUnitPlatformProvider.java:124)
	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)