This test is a flaky failure for iOS and macOS, however I only see the macOS failure internally but they have the same diff and the iOS failures.
The failures seem to be sporadic as you scroll back through the history where you can see periods of the test failing more often, and periods of it not failing at all.
Created 121 cues.
-EXPECTED (missedCueCount < '50') OK
+EXPECTED (missedCueCount < '50'), OBSERVED '60' FAIL
END OF TEST
Set expectations here: https://trac.webkit.org/changeset/262008/webkit