I have an 820 with the same issue. I took it to my dealer, and had a heavier spring put on it. The next quilt was beautiful, not a skipped stich in sight. I was so excited. The next quilt was a batik, and my "masterpiece" so far in my quilting career. It skipped a few stiches once in a while, but had no pattern to it, and I could go several passes without any skipping, so I started to think it was the fabric. The next quilt, I had a few skipped stiches at the beginning and then it was fine. This last quilt, that was a not a batik, I had a few, but did not see a pattern to it. I need to quilt a batik top and see if it gets worse. I use a 90 microtex needle. I clean and change needles after every quilt. I read the posts to this thread with great interest. I am curious to see what others with the same issue have discovered.