Small post to share my painful experience, which may be helpful to someone else.

This case is dependent on your video system, drivers and settings but still, you may be as "lucky" as I was. So before falling in despair read this.

Long story short, at some point I've noticed that character animations are really broken, to the point of making the game unplayable. Let's just say that when I've been looking at at my champions they were twitching like alcoholic hands every minute or so.

I've tried to change different graphics settings, but this combination did the job really well:
- Enable VSync
- Enable Triple Buffering

According to the Internets this is quite common solution, but you should disable any settings inside the game and then forcefully apply them through some software (NVIDIA panel in my case).
Since FE does not have any such options, I guess changing the values in the external software should be enough.
Just be mindful that some settings in the Prefs.ini (like "Fullscreen=1") may still affect the behavior (though I'm not 100% sure).