it might be while its playing via the editor.
probably best to have a try in exporting to test.
if you havent tried exporting anything in Godot as yet, I made a post that might help you at least get to test the game as a windows executable.
How to get your Godot Game up on the web or exe file? - Other Courses / Talk - GameDev.tv
hope that works and the animation looks smoother when exported, but please, let us know how you get on.
DaZ