It appears that you have a tension problem. I know you have tried rethreading, but stay with me and try rethreading one more time. Be sure that your presser foot is UP. This allows your thread to seat properly in the tension disks. Also, according to Kevin Conley (Pfaff educator)hold onto the thread at the spool as you thread the machine with your left hand, holding the thread taut until you reach the needle threader. I hope this solves your problem.