A needle put in backwards will also result in skipped stitches. The flat side of the shaft needs to be where the thread comes out. A friend bought a featherweight and couldn't get it to sew properly. I looked at it and she had the needle inserted so the thread went in front to back. Featherweights are right to left. I moved the needle and it sewed like a dream. I put my needle in backwards (with the flat part to the front) once and it skipped stitches. I've also had an experience where I didn't push the needle in far enough. I've learned to slow down and not be so rammy when I'm changing needles. Now if I could just learn that lesson for the rest of my life...