You may be moving the fabric faster than the eye can read? Also use a soft cloth and make sure the eye isn't fuzzed up with lint. Check your needle to make sure it hasn't developed a burr on the bottom and check to make sure it hasn't slipped down in the needle holder. If the needle isn't good and sharp the slight pause going through the fabric might make it skip? Put a drop of oil on the bobbin case hook in case it needs it. I think I remember something about it not reading well on certain colours but I can't remember which ones. I have never had a problem with mine not reading certain colours. That's all I can think of.