Seen in 606.1.23.1, which is like r233256: When Web Animations is enabled, animations aren’t behaving correctly on some websites, including netflix.com. To reproduce this bug, you’ll need a Netflix account. Log in and navigate to the URL, then hover over the tile for any TV show or movie. The tile will grow and start animating through a slide show, but instead of performing a cross-dissolve from one slide to the next, each slide will fade to black, then the next slide will pop in. Disabling the Web Animations experimental feature makes the issue go away.
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I think the way it is supposed to work is that when you hover over a show, the show's tile will scale up, blend to another general image for the show and then blending into a more specific image for whatever episode you have queued up. For me, on STP 61, the first time you hover over on a show, everything looks fine. However, the second time you do it, you first blend to a black rectangle and then to the queued episode with no blend. My assumption is that the intermediate image is missing and you don't see it blend in and out.
The Netflix design has changed and for me I see videos roll when I hover over a show on macOS. As such I can't reproduce this issue anymore :/