Have you tried sewing with the more expensive threads. I was having an issue with my Bernina activa 230 the patchwork edition which is designed for quilters. The bobbin wasn't sewing right. I was using thread from Walmart. The repair person told me that the more expensive machines are designed to use the more expensive threads, so I switched to Mettler metrosene 100% polyester thread and it has been sewing fine so far. This is just a suggestion. Maybe you can keep your other machine instead of buying a new one.