I have a 8900. What might be happening is that when you use the thread cutter it cuts the threads quite short and the bobbin thread often times barely comes up through the hole. In order for me to grab the bobbin thread I take a stiletto and run it under the raised presser foot and it releases the bobbin thread so I can grab hold of it with my finger tips and pull a longer tail out. What might be happening for you is that if you don't pull a bit of the thread up after cutting, that short piece of thread is bunching up when you start to sew again. I have seen comments from others who have a variety of machines that they use tweezers to grab the thread and pull it up to get more of a lead on it before they begin sewing again. Try pulling a bit of thread up before starting sewing again and see if that solves the problem.