Pia

Bottom first, then upwards to my own file. I have genuinely never been told that.

AttributeError on None is the one I keep hitting and never understood as a category.

I sewed for two years choosing by full bust and blamed my body. It was a drafting assumption.

If it is equal on both sides you are at least consistent, which means it is mechanical rather than technique.

It is a 4.0. I did not realise the width was a factor at all.

I did not know stretch and ballpoint were different. I have used them as synonyms for years.

Ten minutes if I am calm, twenty if I am not. Colour coded thread and doing the loopers before the needles is most of the trick.

I sew about your volume and bought one anyway, and I use it for maybe 20 percent of my seams. I do not regret it but I would not call it a need. Threading it four times still takes me longer than I would admit.

Lay the piece flat and follow a single crosswise thread from the seam to the fold. If it wanders away from the seam line, it was cut off grain.

Also check whether that seam is cut slightly off grain. On a challis that drapes this much, two degrees off is enough to produce exactly what you describe, and nothing you do at the machine fixes a cutting problem.