I had a machine that had problems with bobbin winder, so the bobbins were not would consistently or tightly. Resulted in terrible stitches, skipped stitches,etc. When I took it into dealer to deal with it. I was told that could be everything! He fixed bobbin winder and I was cured. Now, last year I bought a new Elna 720 (same machine as Janoke 6600). Had poor stitch quality, tension was difficult, noisy, and accufeed needle bar seemed to drag when it descended, and I was sure I made a mistake. After 3 months, took it in to Janome dealer to service. They cleaned and 'lubed' machine - it sewed a heck of a lot better than it did out of the box! And the tech told me to add a drop of oil onto the wick when I cleaned thebobbin case (about every 2-3 bobbins depending on thread type). Last but not least,he told me that even schmetz recommends Organ needles if the machine is made in Asia. They are very very slightly shorter. Boy can I see the difference! Can use schmetz but I fight my stitch quality. My machine doesn't like quilting with top stitch needles but does beautifully with isacord or superior and size 12 organ universals or sharps. Think you need to have the machine serviced by Janome service center. Take your a wound bobbin and example of your sewn fabric to show them what's what. Ask for thorough cleaning Top and bottom of machine. Good luck!