I have unpicked more seams that have veered off to the left. My two solutions were to draw a 1/4" seam and sew on the drawn line. The other was to put two 1/4" strips of tape side by side and watch the fabric at the tape instead of the needle. Your eye on the inside of the tape's right edge. Somehow having the second piece of tape in place allowed me to sew a good 1/4". Oh, I have also been known to mark the last 1/2" of the seam line with a marker and ruler when I chain stitch. It's a drag but anything is better than unpicking seams that I have rushed thru.