Can you quantify the valu of the displacement ?
It seems like I have a problem like this with 0.5 millimeter on a drawing of stairs that I draw scale 1:1.
But I'm not sure and didn't pay so much attention, maybe I should.
I would like to know if there is a constant somewhere in your problem. If ever I had the same problem, I could tell you that there is a kind of constancy( if the word exists).