Most of the older sergers have a thread specific threading order. If one thread breaks and it's not the last one that is normally threaded, you must remove all threads and start from the beginning. My Viking Huskylock 1002 LCD was like this and it drove me crazy although it did a beautiful stitch. I switched to a Babylock with the jet air threading and love this machine. Can be threaded in any sequence, and does a beautiful stitch.