The user is the problem..... Mine sometimes goes off to the right, which means that i let go of the right side when coming to the end of the seam- so the last inch of the seam is slightly off to the right, because I still have hold of left. I've done this so many times that I have to make a special effort to keep it straight. I think it is because I'm in a hurry and my right hand is already in position to lift the foot and get the fabric outta there. lol