Checking if there's a known issue but often (but not always!) when I playback in the editor with Unity's timeline I will not get the correct playback in the scene view with spine animations. Which makes it more difficult to set up the animations and blends correctly using timeline.
Sometimes changing the base animation causes it start working on the SkeletonAnimation but sometimes not. Sometimes reloading the scene causes it start, or stop, working (caching maybe?).
The attached screenshot shows a lot of the relevant information. The pose at the bottom is what we expect to play during playback which sometimes happens but often doesn't. The top is the current result. This happens in the scene, in scene prefab mode, and standalone prefab mode.
Interestingly the color change animation does come through so some of the animation is playing back.
Unity: 2020.1.0b13
Spine: spine-unity-3.8-2020-07-30
Spine-Timeline: com.esotericsoftware.spine.timeline-3.9-2020-01-10-beta (maybe can get off of beta)