InvitationTest#testAcceptInvitation and InvitationTest#testGuestActionsOnNonexistantMessage are flickering

org.openqa.selenium.TimeoutException: 
TimedPromise timed out after 300000 ms
Build info: version: '3.141.59', revision: 'e82be7d358', time: '2018-11-14T08:17:03'
System info: host: 'd40da5a00b80', ip: '172.17.0.2', os.name: 'Linux', os.arch: 'amd64', os.version: '4.19.0-16-cloud-amd64', java.version: '11.0.6'
Driver info: org.openqa.selenium.firefox.FirefoxDriver
Capabilities {acceptInsecureCerts: true, browserName: firefox, browserVersion: 92.0.1, javascriptEnabled: true, moz:accessibilityChecks: false, moz:buildID: 20210922161155, moz:geckodriverVersion: 0.30.0, moz:headless: false, moz:processID: 1190, moz:profile: /tmp/rust_mozprofilevuB885, moz:shutdownTimeout: 60000, moz:useNonSpecCompliantPointerOrigin: false, moz:webdriverClick: true, pageLoadStrategy: normal, platform: LINUX, platformName: LINUX, platformVersion: 4.19.0-16-cloud-amd64, proxy: Proxy(), setWindowRect: true, strictFileInteractability: false, timeouts: {implicit: 0, pageLoad: 300000, script: 30000}, unhandledPromptBehavior: dismiss and notify}
Session ID: cb3f7467-c5e0-4180-b552-fba7bff41546
	at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at java.base/jdk.internal.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.base/java.lang.reflect.Constructor.newInstance(Constructor.java:490)
	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.get(RemoteWebDriver.java:277)
	at org.xwiki.test.ui.XWikiWebDriver.get(XWikiWebDriver.java:627)
	at org.xwiki.test.ui.TestUtils.gotoPage(TestUtils.java:710)
	at org.xwiki.test.ui.TestUtils.gotoPage(TestUtils.java:683)
	at org.xwiki.test.ui.TestUtils.gotoPage(TestUtils.java:675)
	at org.xwiki.test.ui.TestUtils.gotoPage(TestUtils.java:625)
	at org.xwiki.test.ui.TestUtils.recacheSecretToken(TestUtils.java:1277)
	at org.xwiki.test.ui.TestUtils.setSession(TestUtils.java:319)
	at org.xwiki.test.ui.TestUtils.forceGuestUser(TestUtils.java:1429)
	at org.xwiki.test.ui.invitation.InvitationTest.testAcceptInvitation(InvitationTest.java:510)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
	at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
	at java.base/java.lang.reflect.Method.invoke(Method.java:566)
	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.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$3.evaluate(ParentRunner.java:306)
	at org.junit.runners.ParentRunner.run(ParentRunner.java:413)
	at org.junit.extensions.cpsuite.ClasspathSuite.run(ClasspathSuite.java:194)
	at org.xwiki.test.integration.XWikiExecutorSuite.run(XWikiExecutorSuite.java:195)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:137)
	at org.junit.runner.JUnitCore.run(JUnitCore.java:115)
	at org.junit.vintage.engine.execution.RunnerExecutor.execute(RunnerExecutor.java:42)
	at org.junit.vintage.engine.VintageTestEngine.executeAllChildren(VintageTestEngine.java:80)
	at org.junit.vintage.engine.VintageTestEngine.execute(VintageTestEngine.java:72)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:107)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:88)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.lambda$execute$0(EngineExecutionOrchestrator.java:54)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.withInterceptedStreams(EngineExecutionOrchestrator.java:67)
	at org.junit.platform.launcher.core.EngineExecutionOrchestrator.execute(EngineExecutionOrchestrator.java:52)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:114)
	at org.junit.platform.launcher.core.DefaultLauncher.execute(DefaultLauncher.java:86)
	at org.junit.platform.launcher.core.DefaultLauncherSession$DelegatingLauncher.execute(DefaultLauncherSession.java:86)
	at org.junit.platform.launcher.core.SessionPerRequestLauncher.execute(SessionPerRequestLauncher.java:53)
	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)