Originally Posted by BonnieJP

My 221s, 99s, 201s, and 66s have a little knob thing at the top of the machine (above and slightly behind the face plate) which is used to adjust the feed dog pressure, I was having the same problem with one of my machines and tightening this knob eliminated the pulling to one side. You might want to try adjusting the pressure knob if your machine has one.