I spotted this intermittent failure in a GHA test run:

2025-05-20T23:00:19.6322480Z TaskEventTest > cancelledCalledAfterHandlerEvenIfConsumed() FAILED
2025-05-20T23:00:19.6424280Z org.opentest4j.AssertionFailedError: expected: <true> but was: <false>
2025-05-20T23:00:19.6521390Z at app//org.junit.jupiter.api.AssertionFailureBuilder.build(AssertionFailureBuilder.java:151)
2025-05-20T23:00:19.6533990Z at app//org.junit.jupiter.api.AssertionFailureBuilder.buildAndThrow(AssertionFailureBuilder.java:132)
2025-05-20T23:00:19.6534680Z at app//org.junit.jupiter.api.AssertTrue.failNotTrue(AssertTrue.java:63)
2025-05-20T23:00:19.6535330Z at app//org.junit.jupiter.api.AssertTrue.assertTrue(AssertTrue.java:36)
2025-05-20T23:00:19.6538610Z at app//org.junit.jupiter.api.AssertTrue.assertTrue(AssertTrue.java:31)
2025-05-20T23:00:19.6539150Z at app//org.junit.jupiter.api.Assertions.assertTrue(Assertions.java:183)
2025-05-20T23:00:19.6540050Z at app//test.javafx.concurrent.TaskEventTest.cancelledCalledAfterHandlerEvenIfConsumed(TaskEventTest.java:428)
2025-05-20T23:00:19.8415740Z
2025-05-20T23:00:19.8585630Z TaskEventTest > onCancelledCalledWhenSetViaProperty() FAILED
2025-05-20T23:00:19.8686890Z org.opentest4j.AssertionFailedError: expected: <true> but was: <false>
2025-05-20T23:00:19.8844360Z at app//org.junit.jupiter.api.AssertionFailureBuilder.build(AssertionFailureBuilder.java:151)
2025-05-20T23:00:19.8958530Z at app//org.junit.jupiter.api.AssertionFailureBuilder.buildAndThrow(AssertionFailureBuilder.java:132)
2025-05-20T23:00:19.9083270Z at app//org.junit.jupiter.api.AssertTrue.failNotTrue(AssertTrue.java:63)
2025-05-20T23:00:19.9200700Z at app//org.junit.jupiter.api.AssertTrue.assertTrue(AssertTrue.java:36)
2025-05-20T23:00:19.9304080Z at app//org.junit.jupiter.api.AssertTrue.assertTrue(AssertTrue.java:31)
2025-05-20T23:00:19.9405900Z at app//org.junit.jupiter.api.Assertions.assertTrue(Assertions.java:183)
2025-05-20T23:00:19.9530260Z at app//test.javafx.concurrent.TaskEventTest.onCancelledCalledWhenSetViaProperty(TaskEventTest.java:375)
2025-05-20T23:00:19.9634970Z

See: https://github.com/kevinrushforth/jfx/actions/runs/15149354795/job/42592721126

I don't know whether this is a test bug or a product bug. It might be related to JDK-8088343.