I saw the following failure one time in our nightly headful test run. It happened to be on macOS, but the failure looks platform-independent. Given where the exception occurs, I suspect that this is a product bug, not a test bug.

TableViewClickOnTroughTest > moveTroughTest() FAILED
    java.lang.IndexOutOfBoundsException: Index -1 out of bounds for length 5
        at java.base/jdk.internal.util.Preconditions.outOfBounds(Preconditions.java:100)
        at java.base/jdk.internal.util.Preconditions.outOfBoundsCheckIndex(Preconditions.java:106)
        at java.base/jdk.internal.util.Preconditions.checkIndex(Preconditions.java:302)
        at java.base/java.util.Objects.checkIndex(Objects.java:365)
        at java.base/java.util.ArrayList.get(ArrayList.java:428)
        at javafx.base@26-ea/com.sun.javafx.collections.ObservableListWrapper.get(ObservableListWrapper.java:88)
        at javafx.base@26-ea/com.sun.javafx.collections.VetoableListDecorator.get(VetoableListDecorator.java:326)
        at javafx.graphics@26-ea/javafx.scene.Parent.updateCachedBounds(Parent.java:1780)
        at javafx.graphics@26-ea/javafx.scene.Parent.recomputeBounds(Parent.java:1724)
        at javafx.graphics@26-ea/javafx.scene.Parent.doComputeGeomBounds(Parent.java:1577)
        at javafx.graphics@26-ea/javafx.scene.Parent$1.doComputeGeomBounds(Parent.java:116)
        at javafx.graphics@26-ea/com.sun.javafx.scene.ParentHelper.computeGeomBoundsImpl(ParentHelper.java:84)
        at javafx.graphics@26-ea/com.sun.javafx.scene.layout.RegionHelper.superComputeGeomBoundsImpl(RegionHelper.java:78)
        at javafx.graphics@26-ea/com.sun.javafx.scene.layout.RegionHelper.superComputeGeomBounds(RegionHelper.java:62)
        at javafx.graphics@26-ea/javafx.scene.layout.Region.doComputeGeomBounds(Region.java:3347)
        at javafx.graphics@26-ea/javafx.scene.layout.Region$1.doComputeGeomBounds(Region.java:166)
        at javafx.graphics@26-ea/com.sun.javafx.scene.layout.RegionHelper.computeGeomBoundsImpl(RegionHelper.java:89)
        at javafx.graphics@26-ea/com.sun.javafx.scene.NodeHelper.computeGeomBounds(NodeHelper.java:104)
        at javafx.graphics@26-ea/javafx.scene.Node.updateGeomBounds(Node.java:3939)
        at javafx.graphics@26-ea/javafx.scene.Node.getGeomBounds(Node.java:3901)
        at javafx.graphics@26-ea/javafx.scene.Node.getLocalBounds(Node.java:3849)
        at javafx.graphics@26-ea/javafx.scene.Node$MiscProperties$3.computeBounds(Node.java:6970)
        at javafx.graphics@26-ea/javafx.scene.Node$LazyBoundsProperty.get(Node.java:10258)
        at javafx.graphics@26-ea/javafx.scene.Node$LazyBoundsProperty.get(Node.java:10249)
        at javafx.graphics@26-ea/javafx.scene.Node.getBoundsInLocal(Node.java:3529)
        at test.robot.javafx.scene.tableview.TableViewClickOnTroughTest.moveTroughTest(TableViewClickOnTroughTest.java:84)