A freind of mine had a simular probem. It was on a Singer 401. She had sewn with it since 1954 and the foot was always crooked. She had taken it to the repair man and he could not fix it. I loosened the shaft that holds the presser foot and re aligned it. It is now perfect. Is this what your machine is doing?
It looks to me like it is set up correct so I don't know what to tell you.