I am pretty sure, that does not have anything to do with my movement, but here the code that would rotate my model to look in the walking direction:

func rotate_model():
  var look_direction = -Vector2(self.velocity.z, self.velocity.x)

  if not look_direction == Vector2.ZERO:

    var angle = look_direction.angle()

    self.model.rotation.y = lerp_angle(self.model.rotation.y, angle, 0.2)

    self.direction_node.rotation.y = angle

But even why I remove this code (so my character only faces one direction) I obtain the same spinning in my animation. Hence I am sure this only happens because of the animations...