My game runs normally at 55-60 fps. But on old devices, when there are too many enemies, the frame rate drops down to ₄₀-45 fps. In those cases, I notice that all spine animations are played slower than normal. I'm not sure if it is how it works, or that is a problem caused by me, because in a different project run by my coworker, the game runs at lower frame rate, usually around 35-40 fps, but the animation speed is just the same as it is in spine editor. Both my project and their one got Application.targetFrameRate set to 60.

I thought spine animation is independent from timescale/frame rate ? I've done some googles and in this topic, someone said that "30 frames would still take one second to play back". As far as I understand, the lower fps, the higher value of Time.deltaTime parsed into SkeletonAnimation.Update(float), which makes the animation advances faster.