If the power goes out while it's tracking a preset, it loses its encoder state.  It doesn't lose its encoder state if the power goes out while it's not moving.  It must then be lowered all the way in the standard reset procedure.   It's not a problem if nothing is under it, but if something is under it, you get to swap boxes or spend a day reorganizing.  

There is a way to swap boxes with another desk which can go all the way down.

1st, lower the donor desk to the bottom height.  2nd move the donor box to the dead desk.  Raise the dead desk as high as possible until it stops.  It won't move anymore.  Return the donor box to the donor desk.  Perform the reset procedure.  Then raise the donor desk as high as possible until it stops.  Move the donor box back to the dead desk & move to the desired height.  Install the dead box in the donor desk.  Perform the reset procedure on the dead box.  

It's unfortunate that the reset procedure requires lowering them all the way instead of raising them all the way.  There is but 1 desk with a donor box & which can go all the way down.  Plugging a desk into a light switch is a bad idea.