I had a problem recently with skipped stitches on a project I was working on. I rethreaded the machine, changed thread, needle etc and the problem still existed. I finally discovered it was the fabric. I was using batik and there were four colors of fabric. I bought all the fabric at the same time from the same place but there was something about the blue one that was giving my and my machine the fritzes. The other colors were fine. I finally changed the tension when I was sewing on the blue and that did the trick so check to see if it is just happening on a particular fabric too.