Welcome aboard Mary Margaret P
I believe this would be called operator error and not any setting. As you treadle the handwheel should continue to spin counter clockwise, or to to the operator. Spinning both ways will break the thread and give you for to many opportunities to thread the needle.
I always tell beginning treadlers not to thread the machine until they can keep a steady rhythm on the treadle while they are talking to someone else. Start by pulling the handwheel towards your self and watching the treadle. try to gently keep that pattern going.
66 is a great machine to learn on I consider it well lubed if I can give the handwheel a spin ( no belts on) for 3 revolutions with a quick flick of my wrist..