The very first reason for the wobbling / bad stitch by your Juki Buttonhole is that there is much oil in your Juki 761 / 762 / 763 Bobbin case and the actual tension of the thread in your bobbin is too strong. You should check this The Second cause is that there is dust or lint which hards plug up the racing surface of hook and the reason become that your stitch is wobbling. The third reason is that Bobbin thread is not neatly wound or thread tension of your bobbin case is too strong The fourth reason is that Needle is not touching the extreme depth of the needle bar hole The 5th reason is that you have not to time the hook of your Juki 761 / 762 / 763 Correctly. Click the link to watch the video here . The 6th reason is that you have done wrong threading . Lint hards plugging up the needle hole of needle plate So check the plates and clean them . The 8th reason is that the tip of your Juki 761 / 762 / 763 LBH Buttonhole is bruised. Change the needle or hook or change both of them.