So i can only speak from my own experience of the last 5 years of trying (and often failing!) to accurately copy or otherwise create various drawings.

Very rarely do I start completely from scratch, but usually adjust the drawing so much that maybe I should have. I wonder if I tracked the adjustments if I would find every line was redrawn in some cases.

Thing is, it is hard to see what part is 'off' until most of the other parts are right. Especially with highly symmetric drawings, where symmetries appear gradually as the whole thing comes together.