Recent failure, Windows x64 job of GitHub Action:
https://github.com/python/cpython/runs/3617689771

0:07:18 load avg: 6.20 [425/427/2] test_concurrent_futures failed (2 failures) (1 min 51 sec)
(...)
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FAIL: test_cancel_futures_wait_false (test.test_concurrent_futures.ThreadPoolShutdownTest)
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Traceback (most recent call last):
  File "D:\a\cpython\cpython\lib\test\test_concurrent_futures.py", line 488, in test_cancel_futures_wait_false
    rc, out, err = assert_python_ok('-c', """if True:
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\a\cpython\cpython\lib\test\support\script_helper.py", line 160, in assert_python_ok
    return _assert_python(True, *args, **env_vars)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\a\cpython\cpython\lib\test\support\script_helper.py", line 145, in _assert_python
    res.fail(cmd_line)
    ^^^^^^^^^^^^^^^^^^
  File "D:\a\cpython\cpython\lib\test\support\script_helper.py", line 72, in fail
    raise AssertionError("Process return code is %d\n"
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: Process return code is 3221225477
command line: ['D:\\a\\cpython\\cpython\\PCbuild\\amd64\\python.exe', '-X', 'faulthandler', '-I', '-c', 'if True:\n            from concurrent.futures import ThreadPoolExecutor\n            from test.test_concurrent_futures import sleep_and_print\n            if __name__ == "__main__":\n                t = ThreadPoolExecutor()\n                t.submit(sleep_and_print, .1, "apple")\n                t.shutdown(wait=False, cancel_futures=True)\n            ']

stdout:
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apple
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stderr:
---

---

======================================================================
FAIL: test_hang_issue39205 (test.test_concurrent_futures.ThreadPoolShutdownTest)
shutdown(wait=False) doesn't hang at exit with running futures.
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Traceback (most recent call last):
  File "D:\a\cpython\cpython\lib\test\test_concurrent_futures.py", line 393, in test_hang_issue39205
    rc, out, err = assert_python_ok('-c', """if True:
                   ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\a\cpython\cpython\lib\test\support\script_helper.py", line 160, in assert_python_ok
    return _assert_python(True, *args, **env_vars)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:\a\cpython\cpython\lib\test\support\script_helper.py", line 145, in _assert_python
    res.fail(cmd_line)
    ^^^^^^^^^^^^^^^^^^
  File "D:\a\cpython\cpython\lib\test\support\script_helper.py", line 72, in fail
    raise AssertionError("Process return code is %d\n"
    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
AssertionError: Process return code is 3221225477
command line: ['D:\\a\\cpython\\cpython\\PCbuild\\amd64\\python.exe', '-X', 'faulthandler', '-I', '-c', 'if True:\n            from concurrent.futures import ThreadPoolExecutor\n            from test.test_concurrent_futures import sleep_and_print\n            if __name__ == "__main__":\n                t = ThreadPoolExecutor(max_workers=3)\n                t.submit(sleep_and_print, 1.0, "apple")\n                t.shutdown(wait=False)\n            ']

stdout:
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apple
---

stderr:
---

---

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Ran 226 tests in 111.014s

FAILED (failures=2, skipped=111)
test test_concurrent_futures failed