The following headful system test fails intermittently on Linux. We see this failure quite often in our automated test runs.

DualWindowTest > testTwoStages FAILED
    java.lang.AssertionError: expected:<400.0> but was:<860.0>
        at org.junit.Assert.fail(Assert.java:89)
        at org.junit.Assert.failNotEquals(Assert.java:835)
        at org.junit.Assert.assertEquals(Assert.java:555)
        at org.junit.Assert.assertEquals(Assert.java:685)
        at test.robot.javafx.stage.DualWindowTest.lambda$testTwoStages$3(DualWindowTest.java:158)