When lines of straight stitching cross over each other, they can cause puckers I am extra vigilant as I get close to an intersection to make sure the layers are all staying nice and flat before stitching over a line. I always start in the middle of a quilt and stitch out to the edge in all directions with my walking foot on my machine. If my quilt has regular blocks with sashing, I do a large grid in this manner before FMQ inside the boxes.