I am using a brother SE 400 for the first time, and thought I had learned how to use it great. after a couple of perfect embroidering jobs, I noticed that the machine is pulling the thread out of the bottom and embroidering with it in some spots of my embroidering. The first few were fine, but now it's messing up every time. It almost sounds like a snag sometimes, and other times it just runs and my pattern goes from purple (the color i was using) to white (thread in the bottom. Please someone help me, i was so excited with my purchase and now I'm becoming discouraged.