Focus stacking (with its layers) wants to be aligned properly. With heavier equipment (like view cameras) and odd angles of inclination for the camera in order to get the shot we want, the sheer weight of the bellows, lens, etc. can at times put stress on the focusing device, making it not always advance smoothly, and its movement causes vibrations..
Quite often, I have to wait for the movement I just made with the focus knob to stabilize and the slight jitter to die down.
I use the Nikon Z7 or Nikon D859. And I wish Nikon would allow me to magnify the object, take the photo, and return to the magnified view. Yet, of course, Nikon does not allow this.
Yet, in magnified view I can clearly see if there is any shimmer in the object, but it is very tedious (and adds further shakiness of its own) to continue to press the magnified view, just to see that shakiness is gone.
And so, a great work-around is to simply add a small bubble level to the hot-shoe on the camera (or wherever). It is very easy to keep an eye on the level and see where there is shakiness and watch it die down. Works perfectly. I can advance the focus steps and keep my eye on the bubble-level and see exactly when there is no longer any movement.
I realize this will interest about zero of you reading this, but there may be a soul or two who stack focus who have not yet found this very helpful tip.