In my opinion the original works perfect!
But.. i had people putting in the key up side down or in the wrong location on the stairs.
I was not able to remove it so i had to break the model to remove the key, had to print a few new new parts because of this.
This modification makes the puzzle easier imo, but will avoid my issue.
The author remixed this model.
Key:
Added a triangle on 1 of the bars of the key to interlock with the ladder.
Ladder:
removed open spaces so there is no way the key will be put into this.
Added a triangle spacing for key mechanism.