I broke a needle and started getting the top thread poking through to the backing. I found and buffed out a couple of burrs on the hook and the needle plate. Now I have a good stitch with good tension but the top thread breaks after 5 to 10 inches of stitching. Help! I have buffed everywhere I can think of to buff. The bobbin thread tightens before the top thread breaks. Could this be a timing issue. I have had the Lenni about 18 months. I am using Signature cotton thread top and bottom. I have replaced the needle. I use an 18 needle.