Old selenium tests (org.xwiki.test.selenium.*) are sometimes failing

java.lang.AssertionError: [//div[@id = 'leftPanels']//div[contains(@class, 'QuickLinks')]] is present.
	at org.junit.Assert.fail(Assert.java:88)
	at org.junit.Assert.assertTrue(Assert.java:41)
	at org.junit.Assert.assertFalse(Assert.java:64)
	at org.xwiki.test.selenium.framework.AbstractXWikiTestCase.assertElementNotPresent(AbstractXWikiTestCase.java:186)
	at org.xwiki.test.selenium.AdministrationTest.testPanelsAdmin(AdministrationTest.java:136)

java.lang.AssertionError
	at org.junit.Assert.fail(Assert.java:86)
	at org.junit.Assert.assertTrue(Assert.java:41)
	at org.junit.Assert.assertTrue(Assert.java:52)
	at org.xwiki.test.selenium.WikiEditorTest.testEditComment(WikiEditorTest.java:109)

org.openqa.selenium.ElementNotVisibleException: 
Element is not currently visible and so may not be interacted with
Command duration or timeout: 10.08 seconds
Build info: version: '2.44.0', revision: '76d78cf323ce037c5f92db6c1bba601c2ac43ad8', time: '2014-10-23 13:11:40'
System info: host: 'localhost', ip: '127.0.0.1', os.name: 'Linux', os.arch: 'amd64', os.version: '3.18.44-vs2.3.7.5-beng', java.version: '1.8.0_121'
Driver info: org.openqa.selenium.firefox.FirefoxDriver
Capabilities [{applicationCacheEnabled=true, rotatable=false, handlesAlerts=true, databaseEnabled=true, version=32.0.1, platform=LINUX, nativeEvents=true, acceptSslCerts=true, webStorageEnabled=true, locationContextEnabled=true, browserName=firefox, takesScreenshot=true, javascriptEnabled=true, cssSelectorsEnabled=true}]
Session ID: 7e77537d-3049-48e8-8532-c489f8fc7b06
	at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
	at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:62)
	at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:45)
	at java.lang.reflect.Constructor.newInstance(Constructor.java:423)
	at org.openqa.selenium.remote.ErrorHandler.createThrowable(ErrorHandler.java:204)
	at org.openqa.selenium.remote.ErrorHandler.throwIfResponseFailed(ErrorHandler.java:156)
	at org.openqa.selenium.remote.RemoteWebDriver.execute(RemoteWebDriver.java:599)
	at org.openqa.selenium.remote.RemoteWebElement.execute(RemoteWebElement.java:268)
	at org.openqa.selenium.remote.RemoteWebElement.click(RemoteWebElement.java:79)
	at org.xwiki.test.selenium.WikiEditorTest.testMinorEdit(WikiEditorTest.java:141)