Spotted in our nightly headful test run:

RegionBackgroundFillUITest > testScenario2 FAILED
    java.lang.AssertionError: expected:rgba(0,128,0,255) but was:rgba(255,255,255,255) at position x=51, y=150
        at test.robot.javafx.scene.layout.RegionUITestBase.assertColorEquals(RegionUITestBase.java:114)
        at test.robot.javafx.scene.layout.RegionUITestBase.runTests(RegionUITestBase.java:398)
        at test.robot.javafx.scene.layout.RegionUITestBase.checkRegionLeftBoundary(RegionUITestBase.java:193)
        at test.robot.javafx.scene.layout.RegionUITestBase.checkRegionLeftBoundary(RegionUITestBase.java:180)
        at test.robot.javafx.scene.layout.RegionUITestBase.checkRegionLeftBoundary(RegionUITestBase.java:176)
        at test.robot.javafx.scene.layout.RegionBackgroundFillUITest.testScenario2(RegionBackgroundFillUITest.java:361)

In looking at past runs, we see a failure in that test about one out of 5 times. It's not always the same test method that fails. I also see failures in the following tests:

RegionBackgroundImageUITest > unalignedImage_PositionCenterBottomRepeatY FAILED
RegionBackgroundImageUITest > alignedImage_PositionCenterFiftyPercentRepeatY FAILED
RegionBackgroundImageUITest > unalignedImage_Contain FAILED