window occlusion was already enabled on MacOS, since MacOS natively supports window occlusion. And video playback on occluded window caused same symptom.
Bug 1759393 Comment 12 Edit History
Note: The actual edited comment in the bug view page will always show the original commenter’s name and original timestamp.
window occlusion was already enabled on MacOS, since MacOS natively supports window occlusion. And video playback on occluded window caused the same symptom.