I must say I have never had this problem. I use Batiks a lot on both the front and back. I use a 16 or 18 needle. The only time I had skipping problems it was because my rollers for the stitch regulator had got off "track". I also use the same thread in the bobbin and top. Have you tried re-threading the machine from beginning to end including the bobbin? Some times that fixes these little "bugs". Good Luck. I am off to my all day quilt group. We meet from noon to 8pm on Mondays. Sometimes I get a lot done and others not.....to much talking and eating.
Connie