I reciently had the same problem with my new Pfaff. Took it back to the dealer and she explained that when the presssure foot is up you are threading the machine, the tension disks inside are open so the thread is able to slide into them properly. WHen you put the foot down, the disks close to hold the thread in w hile stitching. THis is true for almost all machines so.... If you must , thread the machine up to the point of putting thread thru needle, then put foot down to do the last part.