Hello Ixxanubis,
I have rechecked sprite sheet and the aseprite file - everything is fine.
Besides, this animation exists more than 2-3 years and it is first time that there is some kind of such issue.
Can it be related with your game engine?
I just purchased and have the same issue. Using Unity, I threw it into the sprite editor and went about getting it tested, when I noticed the same issue. I've tried slicing it different ways, but still get the shimmy shake. Was there any solution found to this? because I can see it animates properly in a lot of other places.