It might be the piece in the needle plate that makes a rolled edge, if it is extended without the proper presser foot in place it can cause a jamb, usually you will get broken needle (s) also. the loopers are taking ties on the rolled edge piece and not the material and quickly ties down the fabric in the machine, or it just might be threaded wrong and the machine can't figure out what it is doing it gets lost in its own operation so to speak