I have a slant needle 404 singer sewing machine. I have had it for awhile, but unfortunately I can't get it to run properly for long. I have tried different setting, but so far nothing works. For the last setting, I loosened the tension from nuber 3 back to zero and I set it to a larger stitich. It will stitch about 8 inches down the cloth, and then it starts gathering and the bobbin thread gets alll tangled. So I have to cut the fabric from the thread. I'm wondering if a repair man can even fix it? Any advice would be appreciated.