Also, check out the thread. Hold the spool up, let the thread fall down about 12". Is it falling in a nice smooth line or is it twisting and turning and kind of gritchy looking? Whether it is polyester, rayon, or metallic, it should be falling in a smooth line. If it isn't, then you need to change to a thread that is. How it looks is how it will be feeding through your machine, bobbin or top, and it will cause problems if it's not a smooth line.
Also, I have owned 3 Brother embroidery machines, loved them all, but I have found the bobbins are not thread friendly with some brands. I've had the most consistent luck with the OESD bobbin thread. It's a little pricey but I buy the 6,000 yard spools. I also use Sulky bobbin thread. They both work well.