When I deconstructed a ladder when the duplicant above the ladder is waiting for a airlock to be opened, the duplicant is fixed in place with the animation as hanging on the ladder. The duplicant moved went I rebuilt the ladder.
The exact situation was as the picture. I don't have the in-game picture because for some reason the autosave file was corrupted and would not open again.
I think you should try to make the ladder the duplicant is on to be fully deconstructed when the duplicant is still on the ladder. I think it's not the order that matters, its just the problem of the ladder being there or not.