Unity2D: Character goes up and down during idle animation

My character is idling but his feet are changing position during the animation: it seems he’s floating. I would like to have the character with his feet stuck.

Video to visualize the issue: https://vimeo.com/568057364

As you can see, the feet are going up and down. I’ve also tried to animate the collider in order to follow the feet, but that attempt didn’t solve the issue.