Archer30, I also get a "map drawing error" error when trying to replace monsters in !?PI, but only the first time I start the game.
If after that you exit to the main menu and start a new game, there is no error.
I don't know the reason yet.
For some reasons that I will add later (it takes time), I believe that using !!PO will be a better solution than giving artifacts to monsters using !!MO:A.