If you have checked the thread and needles then I would look at maybe for burr along every point that you lace it thru. I had a teeny, tiny one in the hammer hole; my hubby is a machinist by trade and is the one that caught it after hours of frustration on my part. The needles still might be the issue if they were stamped at same time might all have same issue, maybe try a different package of needles. I hope you get it remedied soon.