Same thing happened to mine. The bobbin thread slipped out and was all over the place. I pulled the bobbin casing out and got a magnifying glass. Tiniest piece of lint caught. Cleaned it up and the tension was off. Went to my sisters house and her DGD (quilter in training) same thing with theirs. 4 machines with same problem. Also FW same problem. Needed cleaning and bobbin casing had teeny little pieces of lint missed. I had fun on that FW. Also presser foot needed to be all the way down.