If your first line is not straight, then the bar attachment is going to follow that un-straight line and everything will be off. I would (in future quilts) mark a occasional straightline with cahlk or painters tape so that you have a good reference for "straight", or you can try to follow specific lines in you patchwaork, such as always corssing a specific point on the flying geese as yougo down the quilt orsomething. The walking foot will stitch straight, but the manipulation of the quilt will often throw it off, especially with extra long lines