I would add:
- is your material not on the straight of grain, but biased a bit?
- are you using a seam guide or a flanged foot?
- are you using any starch or Best Press sort of thing, which helps prevent this.
I love my Pfaff because of the IDT -integrated dual technology. It is like have 2 sets of feed dogs, top and bottom, so I don't stretch my fabric when I sew.
ali